A crowd surge at the Astroworld event in Houston, Texas, is believed to have caused the deaths, though local authorities have yet to confirm this.
Videos posted to social media show people rushing the gates of the venue to gain access.
"We had at least eight confirmed fatalities tonight and scores of individuals that were injured," said Houston fire chief Samuel Pena. "At around 9 or 9:15, the crowd began to compress toward the front of the stage and that caused panic and people were getting injured. Houston Fire Department transported 17 people to hospitals."
Police confirmed that 23 people had been taken to hospital, including a 10-year-old. 11 of the casualties were in cardiac arrest.
"Suddenly we had several people down on the ground, experiencing some type of cardiac arrest or some type of medical episode," said Houston Police Executive Assistant Chief Larry Satterwhite. "And so we immediately started doing CPR, and moving people right then, and that’s when I went and met with the promoters, and Live Nation, and they agreed to end early in the interest of public safety."
Astroworld was supposed to occur over Friday and Saturday but today's event has now been cancelled.