A wide stone staircase ascends to the entrance of a light gray administrative building. A large awning of green glass extends above and meticulously trimmed trees sway in the wind on both sides. The entire compound seems perfectly friendly from the outside - even the message over the door.

"Respectfully enforcing the law," it says, "correcting and healing."

The drive from Chongqing to the prison camp Xishanping takes about an hour and a half. The first leg of the journey leads along a large highway to the northwest. Once you cross the Jialing River, though, the road becomes bumpier and the region less populated. It winds up into the densely forested mountains, with only the occasional ruined house dotting the side of the road.

In 2009, back when Li, Xie and Sun traversed this road in a police car, Xishanping was one of the largest prison camps in Chongqing. In its heyday, this 1950s-era facility had up to 10,000 prisoners working inside.

The section of the camp in which Li, Xie and Sun were incarcerated is visible from one side of the street. It is as vast as a small city, with white concrete structures, some five stories tall, rising above brown walls. Many of the buildings are modern-looking and connected by paved streets. Off to one side, in the shade of some tall trees, stands a massive structure with a large iron gate.

Sun was brought to the prison camp on Nov. 13, 2009, with Li and his cousins following three days later. Xie arrived on Dec. 8, 2009. The police brought him straight to the building with the big iron gate.

When he first laid eyes on the building, Xie was reminded of images he had seen years ago on TV, pictures of starving Jews forced to work themselves to death in Nazi concentration camps. Xie describes what happened next:

He was brought into a room where many other new arrivals were squatting on the floor, naked. A guard marched past them, back and forth. It was December and there was no heating. Some of the men were shivering, though Xie couldn't say whether it was due to fear or the cold.

Xie, too, was forced to strip down, squat on the floor, put his hands behind his head and look down. "Squat!" shouted one police officer. "Don't look up!" Then the man inspected Xie's things. The elegant jacket, the modern mobile phone; the officer pocketed his razor. Xie felt helpless - like his rights were being actively disregarded and he couldn't do a thing about it. Impotent rage boiled up inside him.

Once Xie and the rest of the prisoners had been frisked, they were forced to crouch behind each other in a row. Other prisoners who had been there longer shaved their heads and Xie's thick, black locks began to pile up between his feet. He was then handed a pair of light blue canvas pants and a green shirt. They reminded him of clothing that had been fashionable in the 1960s.

Xie, the textile manufacturer, slipped on the plain garb. He was now officially a student of labor camp re-education.

On his second day in Xishanping, Xie became terribly thirsty. He and the other newcomers had been given nothing to drink since their arrival, despite the demanding military training that became their daily routine.

Xie relates how his sense of anxiety only grew. He didn't think they would let him die of thirst, but his body craved water so desperately that rational thinking did little to help.

The newcomers' daily routine was strict. They were forced to run, march and stand still in the cold for five-and-a-half hours. For another five hours, police officers drilled legal texts and camp rules into them.

Admit your mistakes!

Obey your supervisors!

Respect the leadership of the Communist Party!

Day in and day out, the prisoners had to repeat these and other covenants. Even today, Xie can recite the rules from memory.

When a police officer approached a prisoner, the latter was required to drop quickly into a crouch. Outside of lessons, though, the police officers made themselves scarce, delegating many of their duties to selected prisoners, known as "group leaders."

Group leaders enjoyed a number of privileges. They weren't required to take part in morning roll call, for instance, and they didn't have to crouch when a police officer approached. And while normal prisoners ate their meals squatting on the ground, they were allowed to eat at a table and often got extra rations.

Sun says he hated the group leaders and considered them traitors. Li says many of his group leaders were dangerous criminals, adding that the police selected such individuals due to their lack of scruples. Some, he says, took sadistic pleasure in coming up with new forms of humiliation.

The group leaders often addressed the other prisoners as "thief."

Thief, get over here!

Thief, fetch this for me!

Thief, I order you to . . .

The prisoners were expected to answer with, "Yes sir!" They were only permitted to speak with a group leader when he had given them express permission to do so. And visits to the bathroom had to be approved twice.

"Group leader sir, the prison camp prisoner Xie requests permission to use the toilet." That's how Xie had to formulate his requests. If a group leader responded positively, Xie was then required to beg a senior group leader for his permission, too. Only when both had given the green light was Xie allowed to relieve himself. But he wasn't always granted permission.

Xie says there were countless rules for behavior and harassments like this. Some group leaders didn't even tolerate being looked at in a way they deemed unacceptable. And even the smallest rule violations were penalized harshly. A mild punishment could include being smacked on the head or being deprived of food or sleep. There were also so-called stress positions.

Harsher punishments included beatings of all sorts. Sun says he was hit and kicked almost every day because he refused to follow the group leaders' orders. Sometimes he would even attack one of the group leaders himself, pummeling them until reinforcements arrived.

Sun thought he could use his fists to win himself respect and hoped the group leaders would eventually leave him alone. Instead, he was soon introduced to the concept of weiqi, one of the most feared punishments in the camp.

The accounts of our eyewitnesses match those of former detainees in other prison camps who were interviewed by the human rights watchdog Amnesty International between 2009 and 2013. There appears to be a system of rewards and punishments in other Chinese prison camps as well.

Those who obey and serve the police can expect bigger food rations, better sleeping conditions and shorter prison sentences, Amnesty says. In addition to becoming group leaders, selected prisoners evidently played other roles as well.

The zuoban for instance, had to spy on their fellow inmates and report any misbehavior to camp supervisors, Amnesty reports. The dashou, meanwhile, would torture other prisoners.

According to Amnesty, some prison camp leaders used dashou to coerce members of Falun Gong to renounce their beliefs, sometimes using even more brutal methods than those experienced by our witnesses.

One female Falun Gong member reported that two men had removed the skin on the insides of her thighs using nail clippers. She was then forced to crouch for several hours, until a scab had formed and stuck to her pants. The pain when she was finally ordered to stand up, she says, was horrific.

According to Amnesty, prisoners are also subjected to psychological stress. Special courses indoctrinate them about how a proper, law-abiding Chinese citizen is supposed to behave. Political dissidents, Amnesty says, must conduct endless self-criticism, with the aim being that they ultimately believe they are guilty.

Some torture methods hail from the era of China's Cultural Revolution, which took place between 1966 and 1976. Sixiang gaizao was the name of the re-education system back then. Literal translation: Thought reform. Actual meaning: Brainwashing.

On his third morning in Xishanping, Xie could no longer handle the thirst. He needed water immediately and had to do something. He says he didn't care that he might be punished.

Just outside the prisoners' sleeping quarters, at the end of a hallway, was a bucket in which they relieved themselves. Every morning, one of the prisoners was required to empty and clean it.

Xie stood in front of the door to the sleeping quarters, waiting for a guard to unlock it. When one finally did, he bolted. He ran as fast as he could, past the guards laughing derisively and past the other prisoners who evidently had the same idea as him.

Xie grabbed the stinking bucket, carried it to the washroom and cleaned it. Then he drank greedily from the faucet.

After the fourth day, Xie was regularly given enough to drink, but usually there wasn't enough to eat. The menu included cabbage, radish and wax gourd, with meat being a rarity. Often, all they got was a bowl of rice.

Aside from Li, other former prisoners also say they were forced to inhale hot rice while a guard stood behind them and counted down from 10. Sometimes the supervisors would make things even more difficult for them by giving only every second inmate a pair of chopsticks.

During behavioral courses, the prisoners had to sing songs praising the Communist Party. They were meant to help them love China, an instructor once explained to Xie.

"I love my country, but my country doesn't love me," Xie replied.

The instructor fixed his gaze on Xie. "It would be better if you stopped talking immediately."

Xie couldn't sleep that night. Thoughts kept bouncing around in his head. Was his family OK? How would the textile factory manage without him? What would his daughter think of him? When would he finally see her again?

Outside the barred windows of the sleeping quarters, a cuckoo bird was singing. Xie listened to it for a while. He was a little sad when it flew off toward the hills, its call dying away.

After 30 days, Xie was brought to the main area of Xishanping. Multiple guards led him across the massive courtyard. They passed a factory and a number of office complexes before heading into a five-story concrete building and walking up to the second floor.

A guard sat at a table in an outer office, on his left a barred door. Behind it, a long hallway led to 10 dormitories. Xie was assigned to one of them.

The rectangular room was maybe 215 square feet in size and the windows were barred. Three metal bunk beds had been pushed against each wall; Xie was given the top bunk on the first bed to the left. He was not given a mattress or a blanket, only a thin sheet.

There was a box under the bed with the No. 0051 where Xie kept his possessions. He had two pairs of overalls for the summer and two for the winter. He also had two shirts, two pairs of pants, two jackets and two pairs of shoes. He had been forced to buy the clothes at an exorbitant markup, he says.

Once the new arrivals had put away their things, a supervisor explained to them their daily routine. They would wake up at 6 a.m., with their factory shifts beginning at 7 a.m. They would then work until at least 6 p.m., often considerably longer.

The prisoners had Sundays off and would be allowed to shower. They would be permitted to see friends or family twice a month for no more than 10 minutes. At night they were required to stand guard over each other, with two prisoners keeping watch for two hours at a time until morning.

Once the supervisor left, the room fell silent. Xie watched the other prisoners and had the impression that they were trying very hard not to be noticed. Only one of them exhibited fearlessness and defiance. He was tall and had a canine tooth that was crooked and chipped. Judging by his dialect, he was from somewhere up north. The man said he was a truck driver. His name was Sun Jongdae.

Li, Xie and Sun all say the same thing about the work in the factory: It was both monotonous and stressful at once. The prisoners sat at long tables in a big room soldering LAN ports, up to 380 a day, repeating the same few motions over and over again.

They weren't given any eye protection or face masks. Their monthly salary was 8 yuan, the equivalent of just over 1 euro. They were only rarely allowed bathroom breaks.

Those who didn't reach their quota were forced to work deep into the night and too many mistakes would bring down strict penalties. Sun proved rather awkward, frequently soldering the pieces together incorrectly, which earned him beatings from the group leaders. Or he received only one meal a day. Or he was forced to stand in a stress position for hours at a time.

Li was much more dexterous. He had ample experience repairing electronics in his store, so soldering came easily to him. He usually completed his quota before noon. When he had nothing more to do, Li would help the other prisoners, specifically those he considered innocent, such as the old man whose only crime had been stealing a couple of mandarins.

For quite some time, Li couldn't understand why the state would incarcerate people in a prison camp for such minor infractions. But two incidents proved enlightening.

First, he saw a police officer hit a prisoner because he had made a mistake soldering. "I paid a lot of money for you," Li heard the officer say. "Now see to it that you work diligently."

Another time, he overheard a quarrel between a police officer and an evaluator. The latter worked for a company from Guangdong Province that bought some of the LAN ports. The evaluator mentioned that he, too, had paid good money for the prisoners and the quality of their work would have to improve rapidly.

One of Li's fellow prisoners, a man who had been there for a while, told Li how the system of exploitation worked. "The companies pay the camp directors a premium for each prisoner," Li says. "A portion of that premium is then diverted to local police stations to ensure that they keep the prisons full."

Historically, prison camps have always played a role in the economy of the People's Republic of China. Even as far back as 1954, an official document noted that the camps should serve the "economic development of the state." In the 1950s and '60s, prison camp prisoners constructed a huge dam and built long roads and train tracks through remote provinces in addition to other projects.

In today's China, virtually every economic sector profits from forced labor, according to the Laogai Research Foundation (LRF), a now-defunct Washington-based think tank that spent years uncovering abuses in Chinese prison camps.

According to LRF, prison camp prisoners have been used on construction sites and farms, in the machine building and automobile industries, in chemical and battery factories and in asbestos mines. They generally appear to work wherever the task at hand is unbearably monotonous and potentially detrimental to one's health.

Regarding the gross domestic product, forced labor plays only a secondary role: China's gdp reached fully $12 trillion in 2017, whereas the laojiao and other facilities achieved an economic output of several billion dollars.

Still, at the local level, the camps' economic impact is significant. "They're not only profitable for the provincial governments, but also for the camp managers and guards," said Hubert Körper from the International Society for Human Rights.

With such an incentive, officers don't hold back - even arresting a petty mandarin thief if need be.

In addition to working in the factory, the prisoners were often forced to take on special assignments. On one cold January day, Li was carrying two heavy crates of drinks across the courtyard when he saw a new face.

"Hey boss," Li called. "Can you give me a hand?"

The man nodded and took one of the crates. He looked to be in his mid-30s. On his breast was the same tag worn by all the prisoners.

Xie Sunming
Convicted of: Disturbing the social peace
Sector 5
Imprisoned on Dec. 8, 2009

"Why are you really here?" asked Li.

Xie told him about the comment he posted online.

"Then you're not a criminal," Li said.

The two talked for a while, discovering that their dormitories were on the same floor and that Li, too, knew the hot-tempered northerner in Xie's room. He had helped him with his soldering in the factory numerous times.

Li immediately took a liking to Xie. He seemed to be more educated than most of the other prisoners and had apparently once been a successful businessman. Li decided to help the new arrival.

"Watch out for the group leaders," he warned. "Especially He Gang. He is seriously malicious."

In October 2012, residents of Damascus, Oregon, were preparing for Halloween, adorning their front porches in this Portland suburb with spooky decorations. One of those people was Julie Keith.

In her living room, she had a dusty box full of gravestones made of Styrofoam. Keith says she had bought the box two years earlier but hadn't opened it until that Halloween. She had been hoping to surprise her daughter, whose birthday falls shortly before Halloween.

When she opened the box, she discovered a note inside on white lined paper. Someone had written in broken English:

"Sir: If you occasionally buy this product, please kindly resend this letter to the World Human Right Organization. Thousands people here who are under the persecution of the Chinese Communist Party Government will thank and remember you forever."

Keith took a picture of the letter and published it on Facebook, where several media organizations discovered it.

The author, as CNN would later discover, was a 47-year-old member of Falun Gong who had been imprisoned in the notorious Masanjia prison camp in northeastern China until 2010. Prisoners there are alleged to have been subjected to electric shocks and forced feeding through tubes.

The man had made the very Styrofoam gravestones that were now in Julie Keith's living room. During his imprisonment, he had managed to hide around 20 such notes in products he produced - in the hope that someone would find them and set him free.

The surreptitious message that Julie Keith discovered at her home in Oregon is just one of many pieces of evidence proving that China produces goods in prison camps that are destined for export. And that these products end up in countries that are legally prohibited from importing them. In the United States, for example, there is a federal law expressly forbidding the import of any product that was manufactured by forced labor.

Importers find it extremely difficult to determine which products were actually made with the use of forced labor. Goods often make their way through a network of sham companies and middlemen before reaching the end consumer.

In the Chinese commercial register, there were, for instance, four companies with the same address as Xishanping at the time of our research. The firms are called: Jinxi Jingmao, Kangben Technology, Maoben Gongmao und Xumao Gongmao.

All four companies list small electronic parts as their primary business - the very products that Li, Xie, Sun and Wang Shangcai were forced to manufacture between 2009 and 2010 in Xishanping. All four also list the additional business purpose of trade in auto parts, exactly the products that Li's cousin Wang Shangjin assembled in Xishanping.

All four firms were owned by the same holding company: the Yong Zhu Group. This company, in turn, was controlled by a single shareholder: the Committee for Re-education through Labor of the city of Chongqing. Among the management board members was the director of Xishanping.

Most governments don't even try to block such goods from being imported. Besides the U.S., there aren't many countries with official embargoes on wares produced with forced labor. Canada and New Zealand have such laws on the books, but the European Commission still hasn't been able to push through an import ban.

There also have been reports about products manufactured in Chinese forced-prison camps finding their way into Germany. In 2012, for example, a former prison camp prisoner told DER SPIEGEL that he had worked in a laojiao in the Fuling district of Chongqing, manufacturing light strings for export to Germany.

The German government has said that it addresses the system of forced labor, torture and brain washing in high-level talks with the Chinese leadership and during discussions within the structures of United Nations. In the mid-November, German Foreign Minister Heiko Maas publicly voiced his concerns about the grievances in the Uighur province of Xinjiang.

"We cannot accept re-education camps," Maas said at the beginning of a two-day visit to China. In response, the Chinese Embassy in Berlin complained of "blatant interference in the domestic affairs of the Chinese state and a gross violation of its sovereignty."

The 47-year-old Chinese man, however, whose handwritten letter was discovered by Julie Keith, was able to flee China. He sought asylum in the Indonesian capital of Jakarta in January 2017 and shortly thereafter, he wrote Keith an email. After more than four years, she finally learned his name.

In March 2017, Keith flew to Jakarta to meet Sun Yi. At their first meeting, she gave him one of the Styrofoam gravestones as a gift.

The other gravestones have become part of her annual Halloween decorations. It is her way of trying to dignify the suffering that went into their production.