Federal prosecutors are looking into the role played by Carl C. Icahn, the billionaire investor, in advising the Trump administration on regulatory issues that had the potential to affect the finances of a company he owns.
Mr. Icahn stepped down as an unpaid adviser to President Trump in August, after scrutiny from members of Congress about whether he was influencing regulations on ethanol to benefit his financial investments.
One of Mr. Icahn’s main investment companies, Icahn Enterprises, disclosed in a regulatory filing on Friday that federal prosecutors in Manhattan had served a subpoena seeking information about “Mr. Icahn’s activities relating to the renewable fuels standard and Mr. Icahn’s role as an adviser to the president.” The filing said Icahn Enterprises was cooperating with the prosecutors’ demand for information.
