A Chinese scholar who helped an activist escape house arrest has been arrested on the charge of operating an illegal business, nearly three months after he was taken into police custody, his lawyer said Wednesday.

Guo Yushan, founder of the nongovernmental think tank Transition Institute, was arrested on Saturday, said the lawyer, Li Jin.

In 2012, Guo helped the blind activist Chen Guangcheng travel to Beijing after Chen escaped from house arrest in an eastern Chinese village. Chen's daring escape and his recounting of brutal treatment by local officials embarrassed the Chinese government just as it was preparing for high-level China-U.S. talks.

While in Beijing, Chen sought shelter in the U.S. Embassy, and Hillary Rodham Clinton, then the U.S. secretary of state, managed to negotiate for him to go to the United States.

Guo's Transition Institute conducted research on social and economic issues in China, but Beijing authorities, citing lack of proper registration, shut down the organization in 2013.

Guo was detained at a time when Hong Kong protesters were demanding universal suffrage in elections for the semiautonomous city's top official. Dozens of other people also were detained for showing support for the protesters.

It is unclear whether Guo's arrest is related to the Hong Kong protests. He is not known to have made any public comments in support of the pro-democracy movement.

Beijing police did not immediately respond to a faxed request for comment on his arrest.

Li, the lawyer, declined to discuss the charge, saying she had yet to meet with Guo in detention.