Activist shareholder Carl Icahn is being examined by federal authorities in an insider trading probe that also includes golfer Phil Mickelson and Las Vegas sports bettor William “Billy” Walters, according to published reports.

The Journal reported that the FBI and the Securities and Exchange Commission are examining whether Icahn tipped off Walters about his investment plans in a publicly traded company, and that Walters then passed on a tip to Mickelson.

A spokesman for Icahn could not immediately be reached, but Icahn told the Journal that the suggestion that he was involved in improper trading was “illicit and speculative.” He also said they “do not know of any investigation.”

A spokesman for the SEC declined comment.

Icahn’s most recent major action against a Hollywood company was a takeover attempt of Lionsgate in 2010. The studio in March settled an SEC claim that it failed to disclose all information about its effort to stop Icahn, which it ultimately did. The settlement was for $7.5 million, and Icahn afterward unleashed a volley of criticism, calling the studio “Liar Gate,” on his Shareholders Square Table Blog.

The SEC action against Lionsgate represented the first time in nearly three decades that the SEC had filed an enforcement action against a target of a hostile takeover under its tender offer rules.