The move, reported by an assistant, came just days after Ai announced plans to open a studio abroad.
Ai helped design Beijing’s famed Bird’s Nest Olympic stadium but is also an outspoken critic of the government. He said last week he would set up a studio in Germany to show his work, to avoid what he called an increasingly difficult situation in his homeland.
Internet postings Sunday on Twitter, which appeared to be written by one of Ai’s assistants, said police executed a search warrant at the artist’s studio in the Caochangdai district of Beijing, and took away eight staff members for questioning.
China launched a massive crackdown on dissidents and other activists in February, following online calls for anti-government protests in Beijing, Shanghai and other cities. The protests never materialized, in large part because of a large pre-emptive police presence in areas designated for the demonstrations.
The Associated Press said some two dozen uniformed and plainclothes officers could be seen Sunday afternoon in and around Ai’s studio.
Late last year, Ai was stopped from boarding a flight to Seoul, shortly after being invited to attend the Nobel Peace Prize ceremony in Norway honoring jailed Chinese dissident Liu Xiaobo. Liu is serving an 11-year prison term on charges of subversion.