A rights activist who spoke out about abuses she suffered inside the notorious police-run Masanjia labor camp has died in the custody of authorities from the northeastern Chinese province of Liaoning, raising suspicions she was murdered. Chen Shenqun, 58, had been detained while petitioning in Beijing and held at the Majialou detention center on the outskirts of the Chinese capital, before being escorted home by police from her home district of Sujiatun in the provincial capital Liaoyang on Nov. 20. She died en route sometime before the morning of Nov. 21, and police have reported her death as being caused by a "road accident." But Chen's sister Chen Shentie, her brother and ex-husband are now under arrest in a children's hospital in Jinzhou city, fellow petitioners told RFA. Calls to Chen Shentie's cell phone resulted in a switched-off message on Tuesday. Chen's close friend Tang Xinbo said she believes police killed her, however. "She was a petitioner, and it's probable that the police did away with her," she said. "The Sujiatun police were bringing her home from Majialou at the time, and it happened on the way back." "When her sister Chen Shentie went to inquire about it, the local authorities slapped 'stability maintenance' measures on her," Tang said. "They wouldn't let her see Chen Shenqun's body." Video footage seen by RFA showed uniformed police roughing up and detaining family members outside a hospital building, and threatening a man who commented that they were "like the mafia." Cremation before autopsy Family members appeared to be trying to prevent employees of a funeral home, who had heavy backing from police, from taking Chen's body for cremation. Sources said around 10 people were detained following the fracas. Calls to the Liaoning provincial police department rang unanswered during office hours on Tuesday. Online activist Honghong Huohuo said she was previously in touch with Chen's sister, but that all contact had now been cut off. "They were all placed under house arrest at around 11.00 p.m. yesterday evening, in a local guesthouse, and their phones have all been confiscated by the authorities; nobody's picking up," Honghong Huohuo said. "According to the news that's coming out, not a single family member has been allowed to see the body." Chen's death has sent shock waves through the community of fellow petitioners in Beijing, many of whom have pursued complaints against their local government for years, and who have been themselves targeted for arbitrary detention, beatings, and other forms of harassment. Friend and fellow petitioner Jiang Jiawen said she had told the family to try to take photos of Chen's body, and not to allow it to be cremated before an autopsy had taken place. "I also called on fellow petitioners to gather at the crematorium to show support and act as observers," Jiang said. Jiang said she doesn't believe the official account of Chen's death either. "If it was a car crash, the people who were in the car with her would be hurt too, but they only had very light injuries," she said. "There are so many questions surrounding her death ... and we think she was murdered." Torture and mistreatment at Masanjia Tang, a petitioner from Tianjin, said she had campaigned alongside Chen for many years. "She started work in 1976, and worked until she was laid off on March 30, 2003, and she wanted it to be regarded as early retirement, but they informed her in October 2004 that officials can't take early retirement," Tang said. "They cut off her salary and then they sent her to labor camp for a year and a half because she lodged a complaint," she said. "She was in Masanjia for 18 months." "We were really good friends, and we were together in the days before her death." Sources said Chen was tortured and mistreated in Masanjia, including with electric batons. After she got out, she was sent to a local psychiatric hospital, and repeatedly held under house arrest or under police surveillance. A Chongqing-based petitioner surnamed Song said petitioners believe Chen was beaten to death by police on the way back from Beijing. "They beat her to death ... and then they made it look like a traffic accident," Song said. "Her sister and brother were placed under residential detention by the government after they tried to view her body." Fellow former Masanjia inmate Shi Junmei said she shared a cell with Chen in the now-shuttered police-run "re-education through labor" camp. "I was in the same room as Chen Shenqun in 2008. We were serving 're-education through labor' sentences together," Shi said. "Somebody committed identity fraud and impersonated her to steal her salary," she said. "That's why she spent all those years petitioning." Widespread abuses exposed Former inmates have detailed a regime of daily torture and abuse, failure of medical care, and grueling overtime at Masanjia, a former police-run facility where women regarded as troublemakers by the authorities were sent without trial for up to four years at a time. China's National People's Congress (NPC) voted on Dec. 28, 2013, to end the system of administrative punishments known in Chinese as "re-education through labor," or laojiao, but lawyers and inmates' families say many of the camps are still in operation under a different name. In 2014, former Masanjia inmate Liu Hua was criminally detained after she took part in a harrowing documentary that exposed widespread abuses at the camp. In the film, titled "Above the Ghosts' Heads: The Women of Masanjia Labor Camp" and directed by Du Bin, Liu described how camp guards beat the female detainees, used electric batons to shock their breasts, inserted the batons and poured chilli peppers into their vaginas and put them into various torture devices such as "the Death Bed" and "the Tiger's Bench." A former Masanjia inmate recently told RFA that many of the women sent to the camp have since died of various cancers. China's army of petitioners say they are routinely targeted for beatings, harassment and extrajudicial detention if they persist in their complaints. Activists in the southwestern province of Sichuan last week raised concerns over the death in custody of 68-year-old petitioner Yang Tianzhi, also as he was being escorted home from Beijing by "interceptors" from his hometown. Yang's mutilated, headless body was found at the side of a road in Sichuan's Yuechi county town on Aug. 17. Police detained nine suspects at the time, but there have been no developments on the case since, activists said. Government officials declined to comment on the case when contacted by RFA.