McGregor has been with his fiancee Dee Devlin ahead of a scheduled 180km charity voyage across the mediterranean sea.
The former two-weight UFC champion was set to partake in the event alongside Charlene, Princess of Monaco in a bid to raise awareness for water safety, but has now had to withdraw.
AFP news agency says the Irishman has been taken into custody on Saturday, September 12 following a complaint that was filed on September 10 – alleging he was responsible for “acts that could be described as attempted sexual assault and sexual exhibition”.
A statement from the prosecutor read;
Following a complaint filed on September 10 denouncing acts that could be described as attempted sexual assault and sexual exhibition, Mr. Conor Anthony McGregor was the subject of a hearing by the services of gendarmerie, under the regime of police custody.
No other details have been given on the charges against him at present.
The Dubliner has not fought since he beat Donald Cerrone inside 40 seconds in January.
His plans to fight three times this year were shattered by the coronavirus crisis and he retired in June for the third time in four years.