Chinese authorities said today that a U.S.-based scholar arrested in China while researching one of the darkest periods in Chinese history has confessed to taking documents containing state secrets out of the country illegally.

Song Yongyi, a librarian at Dickinson College in Pennsylvania who is widely recognized as an authority on China's 1966-76 Cultural Revolution, was detained Aug. 7 and charged last month with buying and supplying intelligence for people overseas. Foreign Ministry spokesman Zhu Bangzao told reporters today that Song's actions "violated the criminal code of the People's Republic of China and jeopardized state security."

"Song himself has confessed everything related to the facts of the crime; judicial organs are now attentively handling this case," the spokesman said at a briefing.

Song's case has generated an outpouring of support from scholars in the United States and other countries, who see it not only as a violation of Song's rights, but also as a potential threat to their freedom to conduct research in and on China.

About 100 scholars have written to President Jiang Zemin urging him to free Song, a Chinese citizen who has lived in the United States for 10 years and was to have become an American citizen last September. Dickinson professors and students recently delivered a petition bearing 4,400 signatures to the Chinese Embassy in Washington.

Song's wife, Helen Yao, said she does not believe her husband confessed. "I don't think he would confess, because he didn't do anything wrong," Yao said in a telephone interview from Pennsylvania. She said Chinese authorities have denied her husband his right to have a lawyer.

"Our 18-year-old daughter . . . doesn't understand what China is like," Yao said. "She asked, 'Why can't Dad call us from jail? Can we mail him medicine?' But they've even returned a birthday card she sent him."