More documents leaked out of China have shown how the one-party state is trying to "wipe the Muslim Uighurs... off the face of the Earth".
A week after the New York Times released hundreds of files exposing the inner workings of the secretive camps - which China says are voluntary and for reeducation - more have been revealed, this time detailing exactly what goes on behind closed doors in the western Xinjiang region.
They reportedly include a memo from one of the Communist Party's top officials in Xinjiang saying no one should ever be allowed to escape.
According to BBC's Panorama programme, which has sighted the documents released by the International Consortium of Investigative Journalists (ICIJ), the memo also tells staff to "increase discipline and punishment of behavioural violations", "promote repentance and confession" and "encourage students to truly transform".
Every aspect of their lives is tightly controlled, including where their bed is, which desk they sit at and when they're allowed to use the toilet, and it is "strictly forbidden for this to be changed".
Students are forced to learn Mandarin, and every corner of their dorms and classrooms is under video surveillance.
Around 1 million people are believed to be held in the camps. The documents show there were 15,000 new arrivals in just one week in 2017, Panorama reports. They're only eligible for release once they've completely transformed their beliefs and speak Mandarin.
Chinese embassies and consulates around the world are also involved, according to the documents, tracking Uighurs who've made it out of China.
"This is an actionable piece of evidence, documenting a gross human rights violation," Human Rights Watch China director Sophie Richardson told the show.
"I think it's fair to describe everyone being detained as being subject at least to psychological torture, because they literally don't know how long they're going to be there."
The ICIJ called the camps the "largest mass internment of an ethnic-religious minority since World War II".
A human rights lawyer told Panorama it was hard to view the camps as anything other than "a mass brainwashing scheme designed and directed at an entire ethnic community".
"It's a total transformation that is designed specifically to wipe the Muslim Uighurs of Xinjiang as a separate cultural group off the face of the Earth," said Ben Emmerson.
China in a statement said the ICIJ's claims were "fake news".
"Xinjiang is a beautiful, peaceful and prosperous region in China. Three years ago, this was not the case. It had become a battle ground - thousands of terrorist incidents happened in Xinjiang between 1990s and 2016, and thousands of innocent people got killed."
The statement said the camps had nothing to do with religion and people are free to come and go as they please. But the leaked documents say if they are allowed to leave - for reasons of illness, perhaps - they're followed until they come back.