Two officials with ties to China's powerful former domestic security tsar Zhou Yongkang have been placed under investigation, Chinese media and officials said, amid ramped-up speculation that Zhou himself is being targeted.
Zhao Miao, a standing committee member of the Communist Party committee in Chengdu, the capital of southwestern Sichuan province, is being investigated for alleged "serious violations" of discipline, according to the party's Central Commission for Discipline Inspection (CCDI).
No further details were given by CCDI in its one-sentence statement, posted Saturday on the anti-graft body's website.
Authorities are also investigating Yan Cunzhang, head of the foreign cooperation department at China's largest oil company, China National Petroleum Company (CNPC), according to a report Saturday by the respected news magazine Caixin.
Yan was taken away by authorities at the end of last week's Tomb-sweeping Festival, also known as Qingming, Caixin reported, citing people close to Yan.
The petroleum industry and Sichuan province are two of the main power bases of Zhou, who amassed huge influence before his retirement from the Communist Party's Politburo Standing Committee in late 2012.
Zhou was head of CNPC in the late 1990s and was party chief of Sichuan from 1999 to 2002.
News of the two latest investigations follows reports last week that Guo Yongxiang, a former Zhou aide and Sichuan vice governor, was expelled from the party for "serious violations of discipline and the law".
Rumours have swirled for months that Zhou himself is being investigated for graft, although Chinese state-run media reports have generally not mentioned him by name and journalists were barred from raising questions about him at Premier Li Keqiang's annual news conference last month.
If the investigation into Zhou is confirmed, it would mark the first time in decades that such a high-ranking figure has been targeted in a formal inquiry, a move that would send shockwaves through China's political elite.
Members of the Politburo Standing Committee have generally been regarded as untouchable even after retirement.
China's Communist Party authorities have been waging a much-publicised anti-graft campaign in the year since President Xi Jinping came to power.
But critics contend that no systemic reforms have been introduced, and that Xi's targeting of Zhou is a move to sideline a political opponent rather than battle corruption.