US and Libyan authorities are probing oil giants including Italy\'s Eni SpA and Total SA of France for their past ties to the fallen regime of Moamer Kadhafi, The Wall Street Journal reported Sunday. The Libyan general prosecutor\'s office is investigating \"Libyan and foreign operators in Libya\" for possible \"financial irregularities,\" the office\'s deputy chief Abdelmajeed Saad told the Journal. In a March letter, which like Saad did not mention any specific allegations against the named companies, the prosecutor\'s office asked the head of audit at Libya\'s National Oil Co. to supply oil-company documents, the newspaper reported. The letter cited oil transactions between NOC and international traders Vitol Group and Glencore International among the documents it was seeking for a probe focusing mostly on Kadhafi-era transactions but also during the civil war up to the present. Eni, which is among the companies being investigated, is the biggest foreign oil actor in Libya. NOC marketing manager Ahmed Shawki told the Journal that the firm and its dealings with foreign firms were under investigation, and that NOC had submitted all requested documents. He said he did \"everything according to the law,\" but would not comment on Kadhafi-era transactions. The US Securities and Exchange Commission has also sent formal requests to Eni and Total about their Libyan businesses, while US oil giant Marathon Oil Corp. said in February that it was asked for documentation about its Libyan operations, the report said. In its annual filing with the SEC, Eni said the US investigation covered a period from 2008 to early 2011 and concerned \"certain illicit payments to Libyan officials, possibly violating the US Foreign Corruption Practice Act.\" Saad told the Journal that in case of any established wrongdoing, \"the fine will be at least double the amount of money\" lost to the Libyan government and will affect the firm\'s ability to secure future contracts.