The former Zhou Yongkang aide placed under investigation for graft this week had cut energy deals with a state oil executive also implicated in the far-reaching corruption probe.
Two mainland newspapers reported yesterday that Hainan vice-governor Ji Wenlin, who on Tuesday night was accused of breaching Communist Party discipline, had worked closely with Li Hualin, a former deputy general manager of China National Petroleum Corporation, the nation's largest oil company.
The corruption inquiries into Ji and Li are among several believed to be part of an unprecedented probe into Zhou, the country's retired domestic security tsar. Li was among three senior China National Petroleum executives targeted by internal party investigators in August.
Zhou's tenure as CNPC general manager in the 1990s made the company a political power base that helped propel his rise to the supreme Politburo Standing Committee. Ji served as Zhou's personal secretary for a decade until he became Haikou party chief and mayor in 2011.
The reports by The Beijing News and the 21st Century Business Herald yesterday said Ji was suspected of wrongdoing in projects between Haikou and Kunlun Energy, a CNPC subsidiary overseen by Li. The reports cited anonymous sources as saying that the two men had close ties.
After Ji moved to Haikou in February 2011, the city signed a 250 million yuan (HK$317 million) transport contract with Kunlun Energy.
Haikou and Kunlun subsequently set up a bus company, and the municipal government supported the energy company in setting up 55 filling stations across the city.
An anonymous source also told the 21st Century Business Herald that Kunlun won the transport contract after Ji met CNPC's former chairman Jiang Jiemin in Beijing in early 2011.
Jiang, another protégé of Zhou, was serving as head of the regulator overseeing state-owned enterprises when he was placed under investigation for corruption in the summer.
Mao Zefeng, a senior assistant secretary to the board of directors of PetroChina, a listed arm of CNPC, declined to comment on the reported ties between Ji and Li.
"Co-operation was between Kunlun and Haikou, not the company and the vice-governor," Mao said. Kunlun Energy was not available for comment.
Several senior CNPC officials have been sacked since August amid President Xi Jinping's campaign against corruption.
The central authorities late last month began briefing officials on the findings of the corruption case centred on Zhou, signalling that one of the country's most significant graft investigations in decades had entered its final stage.
Ji was promoted to deputy Hainan governor last year. By yesterday, his name had already been removed from the provincial government website.