Outspoken government critic Hu Jia has been detained in the latest in a string of moves by Chinese security forces against people linked to activist Chen Guangcheng, reportedly under US "protection".
Just hours after Hu had told AFP he believed his blind friend Chen was safe in the US embassy in Beijing, his wife said on Twitter overnight Saturday that her husband had been taken away by the authorities.
Self-taught lawyer Chen fled on April 22 with the help of supporters from under the noses of dozens of guards, and subsequently recorded a video alleging abuses against him and his family.
China Aid, a group run by former Tiananmen Square democracy activist Bob Fu, said Saturday it had learned from a "source close to the Chen Guangcheng situation" that the activist was now "under US protection".
Hu's wife, Zeng Jinyan, tweeted that "people from the police will come to collect anti-viral medicine. His (Hu's) detention has been extended to 24 hours. I asked where Hu Jia would sleep, they said on a chair."
It was unclear what the medicines were for.
Later Sunday, Zeng said state security officials had called her again, "demanding to see me today to speak to me.
AFP made calls to the police station at which it was believed Hu was being held but officers said they did not know his whereabouts.
Hu Jia, well-known for activism in support of human rights, people living with HIV/AIDS and the environment, was released in June 2011 after more than three months in prison for "attempted subversion of power."
The detention of Hu, who said he had met Chen since his audacious flight, is the latest action by security authorities following his escape.
Human rights groups previously said Chen's brother, Chen Guangfu and Chen Guangfu's son Chen Kegui had been taken into police custody after a violent confrontation early Friday.
He Peirong, one of Chen's supporters who helped transport him to a safe location, was arrested at her home in the eastern city of Nanjing on Friday, Fu previously said.
Chen, 40, won worldwide acclaim for exposing forced sterilisations and late-term abortions under China's "one child" policy, and for using his legal knowledge to help people battle a range of other perceived injustices.
He and his family were put under round-the-clock house arrest after he completed a four-year jail sentence in September 2010. He has said he was being punished for defiantly continuing to speak out.
Locals in Chen's village of Dongshigu in east China's Shandong province expressed disbelief that "the blind man" could flee the intense security surrounding him.
"I have not heard anything about the blind man escaping, there is no way he could escape," a local farmer who regularly passes by the village told AFP.
After his daring escape, Chen recorded a video directly addressing Premier Wen Jiabao, accusing local Communist Party officials by name and condemning the government for their treatment of him and his family.
China Aid said in a statement Saturday "high-level talks are currently under way between US and Chinese officials regarding Chen's status," also calling on the United States to ensure the safety of the activist and his family.
The United States has expressed concern about Chen, who has been blind since childhood, but refused any comment on his whereabouts, underscoring the huge sensitivity of the issue.
A decision to grant Chen refuge could prove a major diplomatic irritant, with US Secretary of State Hillary Clinton and Treasury Secretary Timothy Geithner due in Beijing Thursday for annual talks amid an often testy relationship between the two countries.
Chen's flight came two months after Wang Lijun, former right-hand man of disgraced Chinese leader Bo Xilai, went to the US consulate in the southwestern city of Chengdu and reportedly sought US asylum.
He was turned down, but the incident was highly embarrassing for Beijing and provoked a major political crisis, with just months to go before a key handover of power in China.
The last Chinese dissident known to have been granted refuge at the US embassy was Fang Lizhi, a key figure in the pro-democracy movement who spent a year under US protection after publicly supporting the 1989 Tiananmen protests.