The investigation of Wang Yongchun marked the second time this month an executive of a major government company was the target of such a probe.
The Ministry of Supervision's one-sentence announcement gave no details of the accusations against Wang, who also is general manager of the subsidiary that operates China's biggest oil field, Daqing.
China National Petroleum Corp. is the parent company of PetroChina Ltd., one of the world's biggest oil producers by market capitalization.
"Discipline violations" often refers to allegations of corruption by a government official or manager of a state company.
Wang also served in China's national legislature, according to official Xinhua News Agency.
China's new leader, Xi Jinping, has made a crackdown on corruption and government waste a feature of his first year in power. He has vowed to target both low- and senior-level officials.
On Monday, a court in eastern China wrapped up a five-day trial of Bo Xilai, a former Communist Party secretary of the major city of Chongqing, on charges of corruption and abuse of power.
Also this month, the general manager of state-owned phone company China Mobile Ltd.'s operations in the populous southern province of Guangdong was detained.
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