Mr Gao was given a suspended sentence for subversion in 2006
A Chinese human rights lawyer who returned home earlier this month after disappearing for more than year has again gone missing, his family says.
Gao Zhisheng was arrested and taken into custody in February last year and not heard from for months.
When he reappeared in Beijing, he said he was giving up his campaigning so he could reunite with his family.
His family now they say they have not heard from him since he returned from a visit to Xinjiang 10 days ago.
"We don't know where he is. We have had no contact. We have not been able to get in touch with him for a month," his sister told the AFP news agency.
Li Heping, a fellow lawyer, told the South China Morning Post Mr Gao had gone to visit his father-in-law in Urumqi, the capital of western Xinjiang region, in early April but was arrested after one night and taken away by police and reportedly put on a plane to Beijing.
"After he got off the plane no one knows where he went," Mr Li told AFP.
"A lot of his friends and colleagues fear that he could have been taken back into police custody."
Mr Gao, who has represented some of China's most vulnerable people, was once named one of the country's top lawyers.
He was charged with subversion by Beijing in 2006 but given a suspended sentence and is not believed to have been charged again during his disappearance.
At a news conference following his reappearance earlier this month, Mr Gao said he was giving up campaigning for the sake of his family.