The investment firm controlled by the billionaire activist investor Carl C. Icahn has fielded questions from federal prosecutors about its management and operations, according to a securities filing made on Wednesday.
On May 3, federal prosecutors in Manhattan requested documents from Mr. Icahn and his firm just one day after his publicly traded company, Icahn Enterprises, became a target of Hindenburg Research, the short-seller firm that has made its name in recent years by taking on the Indian tycoon Gautam Adani and the Twitter co-founder Jack Dorsey.
News of the inquiry was the latest setback for Mr. Icahn, who is best known for targeting publicly traded companies and their chief executives and pressuring management to make changes.
Short sellers profit when stock prices fall, and shares of Icahn Enterprises have fallen nearly 40 percent since Hindenburg Research released a report last week, accusing the company of running “Ponzi-like economic structures.” On Wednesday, the stock fell about 15 percent on news of the federal inquiry.