At least 8 people died on Friday when concertgoers "began to compress" to the front of the stage at the opening night of Travis Scott's two-day Astroworld music festival in Texas.
The crowd moved closer to the stage during the rapper's performance, resulting in a surge, with hundreds injured.
The fire and rescue service took many to nearby hospitals, with around 11 of them in cardiac arrest, while at least eight people have been reported dead, according to Sky News.
"People started to fall out, become unconscious, and it created additional panic," Chief Samuel Peña said during a press conference, per New York Post, calling the occurrence a "mass casualty incident".
The show was called off shortly after, and the second day of the festival was cancelled.
Entertainment company LiveNation organised the event and said they and Scott are cooperating with law enforcement.