BOSTON (Reuters) - Federal prosecutors in Manhattan asked billionaire investor Carl Icahn’s company for information about trades in crane maker Manitowoc, Icahn Enterprises disclosed in a regulatory filing on Thursday, in its first acknowledgement of such a probe.

Billionaire activist-investor Carl Icahn gives an interview on FOX Business Network's Neil Cavuto show in New York, U.S. on February 11, 2014. REUTERS/Brendan McDermid/File Photo

Icahn Enterprises said it received a subpoena after critics questioned the timing of Manitowoc stock sales Icahn, who briefly served as an unpaid adviser to U.S. President Donald Trump, made before his administration announced steep steel tariffs in March 2018. Questions had swirled about whether the sales were prompted by inside information about Trump’s plans.

The stocks of many U.S. industrial companies, major consumers of steel, fell that day after the announcement, with Manitowoc losing more than 6%.

Prosecutors in the U.S. Attorney’s Office for the Southern District of New York contacted Icahn Enterprises in June 2018, the company said in the filing. “We cooperated with the request and provided documents in response to the subpoena.”

The U.S. Attorney’s office and Icahn’s office had no immediate comment. Manitowoc did not immediately respond to a request for comment.

Prosecutors in Manhattan have a history of pursuing major cases over insider trading on Wall Street, famously securing the trial conviction of hedge manager Raj Rajaratnam and a guilty plea from the hedge fund SAC Capital Advisors.

Icahn sold roughly one-third of his stake in Manitowoc, which uses steel to make its equipment, between Feb. 12 and Feb. 22, 2018. Trump said on March 1 that he would impose 15% tariffs on steel imports and 10% on imported aluminum to make domestic production more attractive.

In response to news reports about his stock sales, Icahn said he cut his position in Manitowoc for “legitimate investment reasons” and dismissed any speculation that his sale of shares was prompted by knowledge about Trump’s plans.

Icahn, who has been friendly with Trump for decades, has been a sounding board for Trump and was instrumental in vetting people for key positions before Trump was inaugurated in 2017.

He stepped down as an unpaid special adviser to Trump in August 2017.