NEW YORK — Conor McGregor was involved in a backstage melee Thursday after a news conference for UFC223, and video footage appears to show the promotion’s biggest star throwing a hand truck at a bus full of fighters, injuring at least one who is scheduled to compete Saturday.

Conor McGregor

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

The New York Police Department said it’s investigating.

McGregor hasn’t fought for UFC since November 2016 and was stripped this week by the group’s president, Dana White, of the 155-pound title he never defended. White also said this week he didn’t expect McGregor to attend Saturday’s fights.

McGregor profanely responded on Twitter and wrote, “You’ll strip me of nothing.”

McGregor last fought in a boxing loss to Floyd Mayweather Jr. last Aug. 26.

McGregor is tight with a 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. Chiesa is scheduled to fight Anthony Pettis.

White said this week in New York that McGregor would fight again for UFC this year. McGregor’s actions now put any future fights very much in doubt.

McGregor, 29, once held the 145- and 155-pound championships at the same time, and boldly stated he wanted an ownership stake in UFC.

But McGregor has been out of the fight game except for his boxing dalliance with Mayweather that made him wealthy enough to never have to fight again.

McGregor and his girlfriend welcomed their first child, a son, in May 2017.