A crush at the Astroworld music festival in the southern U.S. state of Texas left at least eight people dead and several injured on Friday night, authorities said.

Houston fire chief Samuel Pena said the incident began at around 9 p.m. when "the crowd began to compress towards the front of the stage."

"That caused some panic and it started causing some injuries, people began to fall out, become unconscious and it created additional panic," Pena said at a press conference outside NRG Park.

"We had at least eight confirmed fatalities tonight and scores of individuals that were injured," he said, adding the cause of death cannot be confirmed until after medical exams are completed.

"We transported 17 patients to the hospital... 11 of those that were transported were in cardiac arrest," he said.

Around 50,000 people were in the crowd at rapper Travis Scott's Astroworld Festival, Pena added.

Houston police said they were investigating the cause of the mass casualty incident and looking at video footage from the arena.

"Over the course of just a few minutes, suddenly we had several people down on the ground experience some type of cardiac arrest," police said, adding the concert was ended after the incident occurred.

Astroworld is a two-day music festival that was scheduled to take place Friday and Saturday in Houston. The event was sold out, according to the Astroworld website. Saturday’s performances have been canceled.

Drake joined Travis Scott on-stage at the concert — which was live-streamed by Apple Music — and posted photos to Instagram after the performance.

Event promoters had arranged for medical units to be on scene at the festival, however once the crowd surge began, those units were “quickly overwhelmed,” Peña said.

In a video posted to social media, Scott could be seen stopping the concert at one point and asking for aid for someone in the audience: “Security, somebody help real quick.”

Houston Police Executive Assistant Chief Larry Satterwhite was near the front of the crowd and said it seemed the surge “happened all at once.”

“Suddenly we had several people down on the ground, experiencing some type of cardiac arrest or some type of medical episode,” Satterwhite said. “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.”

Peña said officials did not immediately know the causes of death for the eight people who died. A medical examiner would investigate. It wasn’t clear whether all eight who died were among the 17 that had been transported to hospitals. The deceased had not been identified as of early Saturday.

Officials set up a reunification center at a hotel for family members who had not been able to reach relatives who had been in attendance at the event. Authorities were looking to connect families with festivalgoers who were transported to the hospital, “some as young as 10” years old, Harris County Judge Lina Hidalgo said.

Houston Police Chief Troy Finner called for calm and urged people not to jump to conclusions as to what caused the surge.

“I think it’s very important that none of us speculate. Nobody has all the answers tonight,” Finner said. He added that there have been several rumors surrounding the event that authorities would look into.

“We’re going to do an investigation and find out because it’s not fair to the producers, to anybody else involved, until we determine what happened, what caused the surge,” he said. “We don’t know, but we will find out.”

The Associated Press reached out to a representative for Scott but did not immediately hear back.

Finner told reporters that Scott and the event promoters cooperated with police.

The deadly surge was the most deaths at a U.S. concert since the 2003 Station nightclub fire that killed 100 people in Rhode Island.

Eleven people died and about two dozen were injured in 1979 at a concert for The Who as thousands of fans tried to get into Cincinnati’s riverfront coliseum.