The athlete is under investigation in Ireland after a woman made the claim in December, according to the Times, which cited people familiar with the investigation. He hasn’t been charged with a crime, the newspaper said. A representative for McGregor didn’t immediately respond to a request for comment.

The report comes hours after a surprise tweet from McGregor saying that he was retiring, potentially stripping the UFC of its most marketable fighter.

“I’ve decided to retire from the sport formally known as ‘Mixed Martial Art’ today,” the 30-year-old Irishman said. The statement came as a shock because the former champion told a Chicago television station earlier this month that he was in negotiations for a return to the UFC as soon as July.

McGregor previously had a two-year hiatus from mixed martial arts, or MMA, which began with a disagreement over money and included a dip into boxing and a megafight against Floyd Mayweather.

McGregor’s return to the MMA octagon last year against Khabib Nurmagomedov was a business success if a sporting loss. The fight in Las Vegas was one of the most lucrative MMA events ever held, with about 2.4 million pay-per-view buys, according to Dave Meltzer, the veteran fighting and wrestling reporter. McGregor, however, suffered a submission loss and hasn’t fought since.

McGregor has retired before amid breakdowns in contract talks. In 2016, McGregor said he’d “decided to retire young,” but ultimately returned for future fights.