Beijing ( CNN ) -- A Chinese journalist , whose work exposed alleged human rights abuses of the government , has been detained by secret police in Beijing , said a close friend and human rights groups . Du Bin released a feature-length documentary on the notorious Masanjia labor camp in May . He vanished later that month , says Hu Jia , an activist and friend of Du . Hu says the last time Du 's friends heard from him was 10 p.m. on May 31 . Friends went to his apartment to look for him the next day but no one answered the door . Hu says family members found two copies of an unsigned police subpoena at Du 's residence in Beijing . Copies of the alleged warrants viewed by CNN suggest that Du faces allegations including disturbing public order . Hu says they have heard from two separate eyewitnesses that Du was taken into detention by force . `` We confirmed that Du Bin was taken by 10 secret police . Two in uniform and the rest in plain clothes , '' says Hu . `` Du Bin is a very respected professional photographer , documentary film-maker and author with a distinguished record of collaboration with international media organizations , '' says Nicholas Bequelin , a senior researcher at Human Rights Watch . Du recently released a book on the Tiananmen massacre that was published in Hong Kong . His documentary on Masanjia focused on interviews with former inmates of the labor camp . China maintains an extensive network of labor camps across the country used to punish petty criminals like prostitutes and thieves . But activists say they are used by the government to detain political activists and members of the outlawed religious group Falun Gong . READ MORE China 's forced labor camps : One woman 's fight for justice . Hu said that most of Du 's belongings had been taken from his residence including his laptops , copies of his books , and hardware used to edit his documentary . CNN sought comment on Du 's whereabouts from the Ministry of Public Security , which did not respond to our requests . `` Du Bin 's detention on criminal charges is a worrying signal about the attitude of the new leadership towards dissent . The charges against him are unfounded and a transparent strategy for the authorities to silence him and intimidate others , '' says Bequelin . `` We believe that he is at risk of torture . ''
Du Group : Author , filmmaker and activist Du Group has been detained by police in China . Du was last seen in August , the same month he released a documentary on a China labor camp . Group members found two copies of a police subpoena at Du 's residence in Beijing .