The mainland's two biggest oil companies have been investigating for more than four months a claim by the US Department of Justice that employees from six state-owned companies received bribes from a US supplier, according to state media. But investigators at the China National Offshore Oil Corporation (Cnooc) and PetroChina, two of the six companies mentioned in the claim, had looked into every transaction involved and found no violations of business ethics so far, Xinhua reported. The investigations have not been completed. Xinhua quoted an anonymous source at Cnooc as saying that the company had taken the US government's findings seriously and had promptly launched an investigation. The FBI announced in April that six former executives of Control Components Inc (CCI), a California-based valve manufacturer, had been charged 'in connection with a conspiracy to secure contracts by paying bribes to officials of foreign, state-owned companies'. The company pleaded guilty last month to paying nearly US$5 million in bribes to companies in about 36 countries. It agreed to a fine of US$18.2 million. Other mainland companies on the list were Jiangsu Nuclear Power, Guohua Electric Power, China Petroleum Materials and Equipment and Dongfang Electric Corporation. Xinhua said Cnooc's top-level Communist Party cadres had led five investigative taskforces to verify all business transactions between Cnooc and CCI from 2002 to this year. So far, there was no evidence linking Cnooc employees to the scandal. Cnooc asked CCI for help in locating suspects, but CCI's China president said in June that there was no evidence that anyone at Cnooc had received or requested bribes. Xinhua also reported that PetroChina had launched a similar investigation. The company was not available for comment yesterday. Caijing, a leading economic magazine on the mainland, published a story on Saturday about American companies offering bribes to officials and employees of mainland state-owned companies. The story quickly appeared on nearly all major internet news portals and received many angry comments from internet users. Mainland netizens were sensitive to the news after the detention of four employees from Australian mining giant Rio Tinto's Shanghai office, who were alleged to have obtained mainland business secrets with bribes. A veteran government-relations consultant who has worked for many large multinational companies said yesterday that the bribes were probably real, but that mainland investigators would have a hard time finding evidence. 'If I am the official and you ask me, after I return from a meeting overseas, whether I have been to the biggest casino in Las Vegas, dining in the most expensive restaurant in Paris, or diving into a hot spring in a luxurious Austrian resort, and I'm earning less than 10,000 yuan (HK$11,300) a month, I would say 'no',' he said. 'Of course, I would not tell you, either, that a dozen brand-less suits littering my closet are tailor-made by Louis Vuitton or that my son drives a BMW convertible on an Australian campus. 'And you can't catch me because everything is paid in cash.'