UFC star Conor McGregor has been accused of sexually assaulting a woman during an NBA Finals game last week in Miami, according to legal letters obtained Thursday by ESPN.

The woman said McGregor “violently” forced himself on her inside a VIP men’s bathroom at Kaseya Center, according to a letter sent to McGregor and his team. She said that McGregor “aggressively kissed her” before also attempting to force her into multiple sexual acts.

The incident allegedly occurred during Game 4 of the Finals on Friday. The woman has accused the Miami Heat and NBA security of aiding McGregor in the attack by separating her from her friend and forcing her into the bathroom.

McGregor, 34, denied the allegations through his attorney Barbara Llanes.

Attorney Ariel Mitchell, who is representing the woman, wrote in the letter to McGregor that the woman immediately contacted law enforcement and her law firm after the alleged attack. The letter warned of possible litigation and called for McGregor to preserve all potential evidence. Mitchell also sent legal letters to the Heat and the NBA.

UFC issued a statement Thursday saying it was aware of the allegations against McGregor, adding that it “will continue to gather additional details regarding the incident. UFC will allow the legal process to play out before making any additional statements.”

McGregor was at the game as a guest of the NBA and the Heat, who were playing the Denver Nuggets in the Finals. During halftime of Game 4, McGregor took part in a skit to promote a recovery spray in which he punched Heat mascot Burnie twice, which sent the man portraying the mascot to the emergency room to receive pain medication.

The Heat and NBA both acknowledged the woman’s allegations in statements. The NBA said it was working with the Heat to gather more information.

McGregor has been accused of sexual assault four previous times outside the United States, although he has not faced any legal punishment and at least one case was dropped.