BEIJING — Supporters of human rights activist Chen Guangcheng, who fled house arrest and is reportedly at the U.S. Embassy in Beijing, are now facing police detention, activists in the U.S. and China said Sunday.

The threat of official retribution highlights the complexity of the crisis as U.S. officials are believed to be trying to find a viable solution to the unexpected diplomatic standoff with Beijing. Whether that includes Chen’s friends remains to be seen.

Human rights experts said priority would be given to Chen’s wife and daughter in any negotiations to secure protection. Officials at the embassy and in Washington have still not confirmed or denied that they are keeping Chen, 40, a lawyer who was imprisoned for exposing forced sterilizations and other abuses by authorities and was placed under house arrest after his release in September 2010.

Assistant Secretary of State Kurt Campbell arrived in Beijing on Sunday, days before he was scheduled to appear at a long-planned meeting of senior U.S. and Chinese leaders that includes U.S. Secretary of State Hillary Rodham Clinton and U.S. Treasury Secretary Timothy Geithner.

Among Chen’s network of friends most at risk is Hu Jia, a longtime government critic and AIDS activist who reportedly met with Chen when he arrived in Beijing earlier this week. Hu has been in police custody since Saturday afternoon. Hu’s wife, Zeng Jinyan, was also told to turn herself in for police questioning Sunday, but the mother of one refused.

Hu was held by police without sleep for 24 hours and released late Sunday.

“We don’t want to see anyone hurt or detained because of Chen’s escape,” Zeng said in a phone interview from her home in Beijing. “But supporters who are helping are under pressure.”

The couple, along with He Peirong, a longtime activist from the southern city of Nanjing, and Guo Yushan, a Beijing-based scholar, helped Chen break free from 19 months of house detention — an ordeal imposed without any criminal charges.

He, who surreptitiously drove Chen several hundred miles from his village in eastern Shandong province to Beijing, was arrested Friday, according to human rights workers. Guo has been incommunicado since Saturday. The status of Chen’s wife and daughter remains unknown. His nephew has been detained for allegedly fighting local officials, activists said.

Chinese and American officials are now negotiating what to do with Chen, according to Bob Fu, president of the China Aid Association, a Christian group in Texas that has promoted Chen’s cause.

“At this point, I’m more worried about Hu, He and Guo than Chen Guangcheng,” said Nicholas Bequelin, a Hong Kong-based researcher for Human Rights Watch.

Bequelin said Beijing would have to face significant pressure not to punish those who aided Chen. Hu is especially vulnerable because he remains under so-called political deprivation after serving a prison term for subverting state power.

Joshua Rosenzweig, a human rights researcher in Hong Kong, said Chen’s friends could be facing short-term detention so that authorities can learn how the blind dissident carried out his dramatic escape.

“Often what goes on is round-the-clock interrogation without rest,” Rosenzweig said. “It’s the only window of time police can do anything they want.”