A senior Chinese official is under investigation, a Hong Kong newspaper reported at the weekend, in a case that could represent the first time a national political figure has been netted in China's anti-corruption drive.
Li Jianguo, a member of the country's elite Politburo and the vice chairman of the national rubber-stamp legislature, has not been charged with any offence.
The Hong Kong-based Ming Pao newspaper however reported that Li had checked into a Beijing military hospital due to "psychological stress" from the investigation.
A call to the National People's Congress news department was not answered on Sunday.
If charges do result, Li would be the highest-ranking official snagged in an anti-corruption drive launched by the new party leadership.
Earlier this month, the new head of China's ruling communist party, Xi Jinping, said anti-corruption efforts should target low-ranking "flies" as well as powerful "tigers".
Not all corruption investigations result in charges, and officials rumoured to be under investigation often reappear in public in a sign that their case has been cleared.
Li, who is not a widely known political figure, was formerly secretary to Li Ruihuan, a powerful official throughout the 1990s. He is considered close to the Communist Youth League, the power base for outgoing Chinese president Hu Jintao, and was only named to the Politburo in November.
He spent many years as party secretary of Shaanxi Province before a brief stint as party secretary of Shandong Province.
If charged, Li would be only the fourth member of the Politburo, a powerful grouping of only 25 senior Party members, to be toppled in a corruption scandal since 1995.
The anti-corruption drive has so far implicated mostly regional officials, including the deputy party boss of Sichuan Province, Li Chuncheng, who had for many years overseen development of the province's prosperous capital, Chengdu.
A construction magnate has also been detained in that case.
Li is a common family name in China, and the three Lis are unrelated.