Eight people have died and numerous others were injured in what officials called a “mass casualty incident” at Travis Scott’s Astroworld 2021 music festival in Houston on Friday night, the AP reports. Officials transported 17 people to hospitals, including 11 people who were in cardiac arrest. The medical examiner is currently investigating the causes of death.

“The crowd began to compress towards the front of the stage, and that caused some panic, and it started causing some injuries,” Houston Fire Chief Samuel Peña said during a press conference. “People began to fall out, become unconscious, and it created additional panic.” Peña added that the festival’s on-site medical units were “quickly overwhelmed” following the crowd surge.

According to Houston station ABC13, the crowd began to surge when Drake made a surprise appearance with Travis Scott. One fire department official said the incident “seemed like it happened over the course of just a few minutes.”

“Our hearts are with the Astroworld Festival Family tonight—especially those we lost and their loved ones,” the festival wrote in a statement posted early this morning. 

Astroworld 2021 was set to continue tonight (Saturday), but it has been canceled.