UPDATE: The NYPD tells NY1 Conor McGregor turned himself in and is being detained by police. (11:18 p.m.)

Conor McGregor was involved in a backstage melee, and video footage appears to show the UFC star throwing a guardrail at a bus full of fighters on Saturday's card.

McGregor crashed a press conference Thursday at Barclays Center. Video showed him with a group of people causing chaos as they took an elevator to the loading dock at the arena. He can be seen tossing trashcans and being prevented from throwing a barricade at a bus during his unannounced appearance in New York.

McGregor hasn't fought for UFC since November 2016 and was stripped this week by UFC President Dana White of the 155-pound championship he had never defended. White also said this week he did not expect McGregor to attend Saturday's UFC 223 card.

McGregor profanely responded on Twitter and wrote, ``You'll strip me of nothing.''  McGregor is tight with UFC 223 fighter Artem Lobov, who was involved this week in a scuffle in a hotel with Khabib Nurmagomedov.

Nurmagomedov fights Max Holloway for the lightweight championship left vacant by McGregor.

Lobov was yanked from the card and the fight status of Michael Chiesa was unclear after he was sent to the hospital with injuries sustained in the attack.