Shaoyang city authorities have insisted that activist Li Wangyang's body was cremated at his family's request.
They said Li's ashes were interred under the supervision of his sister Li Wangling and brother- in-law Zhao Baozhu.
The two have been out of reach since Friday. Lawyer Tang Jingling, who is assisting the couple, said they are being held in a city inn.
Shaoyang authorities said four experts from the Sun Yat Sen University were invited to conduct an autopsy on Friday. The university will announce the autopsy report in three to four days.
The authorities claimed the whole process was videotaped and supervised by members of the National People's Congress and the Chinese People's Political Consultative Conference. They said the media were also invited.
They issued a statement claiming that Li's wardmates found him "acting strangely" as he stood near the window around 3am on the day he died, and that there were no other bruises on his body, according to the initial investigation.
"Surveillance camera footage showed that on the night Li Wangyang died, no suspicious persons entered the ward except Li's wardmates and hospital staff," the statement said.
The ward's door was not forced open, it added.
Meanwhile, Li's friend Huang Lihong told RTHK yesterday she saw mainland police forcing Li's family to sign a consent form, agreeing that a post-mortem examination be conducted on Li as soon as possible.
And while Huang did not witness if Li's family agreed to have his body cremated, she did not believe they would have done so willingly.
Huang and other friends of the dead activist have been under round-the-clock surveillance by the Shaoyang authorities.