The chairman of China's biggest oil and gas producer has been questioned by the Communist Party's top discipline watchdog in relation to the Ferrari crash in Beijing earlier this year that claimed the life of the only son of Ling Jihua, party general secretary Hu Jintao's former top aide, sources say. They said the probe into China National Petroleum Corp (CNPC) chairman Jiang Jiemin focused on a large sum of money - several tens of millions of yuan - that was transferred from CNPC to the families of two women injured in the single-vehicle accident. The episode raises doubts about corporate governance practices at CNPC, the giant state-owned energy company. Sources said the party's top disciplinary officials were shocked by the ease with which such a large sum of money could be transferred out of a giant state firm without any accountability or proper documentation. It also raises questions about the oversight capability of government regulators including the State-owned Assets Supervision and Administration Commission, led by Wang Yong. At a group discussion at the party's 18th congress last week among delegates from central government-administered companies and agencies, Jiang sat next to Wang in the front row. Sources said Jiang had been trying to help Ling, then head of the powerful General Office of the party's Central Committee, pay compensation to the families of the other victims and prevent details of the car crash from leaking out to the public. The driver killed in the accident was Ling's only son, Ling Gu. He lost control of the black Ferrari on Beijing's North Fourth Ring Road in the early hours of March 18 and slammed into a wall. He was found dead at the scene, half-naked. Two young women from an ethnic minority - one naked and the other semi-clothed - who were with him in the car were both seriously injured. Ling was one of China's most powerful men whose help Jiang might need to further his career, until a surprise personnel reshuffle in September which saw him moved to head the United Front Work Department - a largely symbolic post. Sources said investigators eventually traced the money back to CNPC. They said that partly explained Jiang's absence from the public eye for a few weeks since late July, which prompted online rumours that he might have fled abroad. In an apparent effort to quell those rumours, CNPC issued a statement on September 4 saying its chairman had participated in a company meeting the day before. Jiang gave an interview to a magazine affiliated with the Xinhua news agency two days later, about a West-East natural gas transmission project. CNPC deputy general manager Wang Yongchun said that Jiang was still in charge of the company despite an illness. "Jiang has been suffering from chronic eye disease," Wang said. "It's not completely cured, but almost." Jiang, a member of the congress's 247-strong presidium, joined the group discussion on Friday, the second day of the week-long congress. Company spokesman Li Zhanbin said he had "not heard anything regarding an investigation", adding that Jiang was still presiding over the company "as usual". Sources said Jiang was indeed in poor health and that the anti-graft probe had worsened his condition. They said the fact that Jiang was a member of the presidium showed that, for the time being, he was likely to be given a clean bill of political health.