Carl C. Icahn, the billionaire investor who was a close confidant of President Trump, has received a second subpoena from federal prosecutors in Manhattan, this one related to a series of stock trades last year.

Icahn Enterprises, one of Mr. Icahn’s main investment companies, disclosed in a regulatory filing on Thursday that it had received a subpoena in June seeking “production of information pertaining to trading in shares of Manitowoc,” a crane manufacturing company.

Icahn Enterprises said it had complied with the request, but it was unclear why the company was disclosing the subpoena only now. There was no mention of it in the 2018 annual report that Icahn Enterprises filed in early March.

The filing did not disclose details of the trades that prosecutors were interested in, but a timely sale of Manitowoc shares in early 2018 prompted questions from the news media. Mr. Icahn, who had previously served as an unpaid adviser to the Trump administration, sold $30 million worth of Manitowoc stock in early 2018, not long before the White House said it was imposing tariffs on foreign-made steel.