A federal investigation is probing whether golfer Phil Mickelson and a high-stakes gambler received illegal stock tips from billionaire investor Carl Icahn, US media reports say.
The FBI and US Securities and Exchange Commission (SEC) are investigating the stock trading patterns of Mickelson and Las Vegas gambler William 'Billy' Walters, alleging they might have been given inside information from Icahn about his investment plans.
The probe is focused on investments the men made in cleaning products maker Clorox, The New York Times and The Wall Street Journal reported. Icahn's company made a takeover bid for Clorox in 2011 that caused stock prices in the company to jump. His bid was ultimately rebuffed and prices dropped.
Walters and Mickelson each made well-timed trades in the company during this period.
This led investigators to probe whether they were acting on information Icahn gave them about his company's takeover attempt.
Insider trading - profiting on the stock market from inside information not available to the general investing public - is illegal.
However, it's not yet clear if Mickelson or Walters were acting on information given to them by Icahn or, if they were, whether Icahn shared any information illegally.
The investigators are also looking into Mickelson and Walters' trading related to another company, Dean Foods, but there is no obvious connection to Icahn, the two papers reported.
Icahn denied the accusations, calling them "inflammatory and speculative".
"We are always very careful to observe all legal requirements in all of our activities," he told the Journal.
A lawyer for Mickelson assured the newspaper his client was not the target of any investigation, and Walters refused to comment.
The SEC and FBI also declined to comment on the case.
Walters and Icahn became friends while Icahn owned a Las Vegas hotel in 1998. The two have spoken about stocks, according to the Journal. Walters and Mickelson play golf together, the paper said, but added Icahn said he did not know the golfer.
US authorities have launched a crusade against insider trading in recent years, which has already resulted in dozens of indictments.