A Chinese local government is deleting data and destroying documents after classified papers were leaked offering information on its mass detention camps for Uighurs and other predominantly Muslim minorities, according to four people in contact with government employees there.

They claimed regional officials in Xinjiang province are also tightening controls on information and have held high-level meetings following the leaks.

Top officials deliberated how to respond in meetings at the Chinese Communist Party's regional headquarters in Urumqi, Xinjiang's capital, some of the people said.

They spoke on condition of anonymity because of fears of retribution against themselves, family members and the government workers.

China destroying Uighur burial grounds Show all 6 1 /6 China destroying Uighur burial grounds China destroying Uighur burial grounds Teywizim cemetery in Hotan (before and after) China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity Earthrise/AFP/Getty China destroying Uighur burial grounds A cemetery in Xayar (before and after) This combo of satellite images received on September 30, 2019 from CNES 2019, distributed by Airbus DS and produced by Earthrise shows a picture from August 29, 2017 (top) showing a cemetery (C) and the same view on July 5, 2019 (bottom) with no sign of the facility in Xayar, Xinjiang province. - China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity in Xinjiang. (Photo by Handout / various sources / AFP) / TO GO WITH China-rights-Xinjiang,FEATURE by Eva Xiao, Pak Yiu, with Andrew Beatty -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / CNES 2019/ DISTRIBUTION AIRBUS DS/ PRODUCED BY EARTHRISE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVES / (Photo by HANDOUT/EARTHRISE/AFP via Getty Images) HANDOUT Earthrise/AFP/Getty China destroying Uighur burial grounds A graveyard in Aksu (before and after) An image of a graveyard in Aksu in 2015, where Uighur poet Lutpulla Mutellip was buried and the same view in 2018 and then again in 2019 showing a new park called "Happiness Park" Earthrise/AFP/Getty China destroying Uighur burial grounds A cemetery in Xayar (before and after) This combo of satellite images received on September 30, 2019 from CNES 2019, distributed by Airbus DS and produced by Earthrise shows a picture from August 29, 2017 (top) showing a cemetery (C) and the same view on July 5, 2019 with no sign of the facility in Xayar, Xinjiang province. - China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity in Xinjiang. (Photo by Handout / various sources / AFP) / TO GO WITH China-rights-Xinjiang,FEATURE by Eva Xiao, Pak Yiu, with Andrew Beatty -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / CNES 2019/ DISTRIBUTION AIRBUS DS/ PRODUCED BY EARTHRISE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVES / (Photo by HANDOUT/EARTHRISE/AFP via Getty Images) HANDOUT Earthrise/AFP/Getty China destroying Uighur burial grounds Sulanim cemetery in Hotan (before and after) This combo of satellite images received on September 30, 2019 from CNES 2019, distributed by Airbus DS and produced by Earthrise shows a picture from April 24, 2018 (top) showing the Sulanim cemetery (C) in Hotan, Xinjiang province and the same view on August 6, 2019 (bottom) with no sign of the facility and it has been replaced with a car park. - China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity in Xinjiang. (Photo by Handout / various sources / AFP) / TO GO WITH China-rights-Xinjiang,FEATURE by Eva Xiao, Pak Yiu, with Andrew Beatty -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / CNES 2019/ DISTRIBUTION AIRBUS DS/ PRODUCED BY EARTHRISE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVES / (Photo by HANDOUT/EARTHRISE/AFP via Getty Images) HANDOUT Earthrise/AFP/Getty China destroying Uighur burial grounds A cemetery in Xayar (before and after) This combo of satellite images received on September 30, 2019 from CNES 2019, distributed by Airbus DS and produced by Earthrise shows a picture from August 20, 2014 (top) showing a cemetery (centre L) and the same view (bottom) on July 5, 2019 where it has been replaced with a a newly built standardised cemetery, in Xayar, Xinjiang province. - China is destroying burial grounds where generations of Uighur families have been laid to rest, leaving behind human bones and broken tombs in what activists call an effort to eradicate the ethnic group's identity in Xinjiang. (Photo by Handout / various sources / AFP) / TO GO WITH China-rights-Xinjiang,FEATURE by Eva Xiao, Pak Yiu, with Andrew Beatty -----EDITORS NOTE --- RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / CNES 2019/ DISTRIBUTION AIRBUS DS/ PRODUCED BY EARTHRISE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS - NO ARCHIVES / (Photo by HANDOUT/EARTHRISE/AFP via Getty Images) HANDOUT Earthrise/AFP/Getty

They continued after the International Consortium of Investigative Journalists worked with news organisations to publish secret guidelines for operating detention centres and instructions on how to use technology to target people.

The Chinese government has long struggled with its 11 million Uighurs, an ethnic Turkic minority native to Xinjiang, a far west province.

In recent years, it has detained one million or more Uighurs and other minorities in the camps.

Xinjiang officials and the Chinese foreign ministry have not directly denied the authenticity of the documents, though Urumqi Communist Party chief Xu Hairong called reports on the leaks "malicious smears and distortions".

The local government did not respond to a fax for comment on the arrests, the tightened restrictions on information and other measures responding to the leaks. The Chinese Foreign Ministry did not have an immediate comment..

Information seems to be becoming more tightly controlled. Some university teachers and district-level workers in Urumqi have been ordered to clean out sensitive data on their computers, phones and cloud storage and to delete work-related social media groups, according to one Uighur with direct knowledge of the situation.

In other cases, the state appears to be confiscating evidence of detentions. Another Uighur who had been detained in Xinjiang years before said his ex-wife called him two weeks ago and begged him to send his release papers to her, saying eight officers had come to her home to search for the papers and threatened she would be jailed for life if she could not produce the papers.

"It's an old matter, and they've know I've been abroad for a long time," he said. "The fact that they suddenly want this now must mean the pressure on them is very high."

Some government workers have been rounded up as the state investigates the source of the leaks.

In one case an entire family in civil service was arrested. Abduweli Ayup, a Uighur linguist in exile, said his wife's relatives in Xinjiang - including her parents, siblings, and in-laws - were detained shortly after the leaks were published, claiming they had no relation to the leaks as far as he was aware.

He said some people in touch with relatives outside China were also investigated and seized.

It is unknown how many have been detained since the leaks.

Earlier this week, a Uighur woman in the Netherlands told de Volkskrant, a Dutch daily, that she was the source of the documents published by the International Consortium of Investigative Journalists.

Asiye Abdulaheb said that after she posted one page on social media in June, Chinese state agents sent her death threats and tried to recruit her ex-husband to spy on her.

The leaked documents lay out the Chinese government's deliberate strategy to lock up ethnic minorities even before they commit a crime and to rewire their thoughts and the language they speak.

They reveal that facilities Beijing calls "vocational training schools" are forced ideological and behavioural re-education centres run in secret.

The papers also show how Beijing is pioneering a new form of social control using data and artificial intelligence. Drawing on data collected by mass surveillance technology, computers issued the names of tens of thousands of people for interrogation or detention in just one week.

Last week, the US.House of Representatives overwhelmingly approved the Uighur Human Rights Policy Act, aimed at pressuring China over the mass detentions in Xinjiang.

Beijing swiftly denounced the bill as foreign meddling.