At least 8 dead and many injured after crowd surge at Travis Scott's Astroworld Festival

At least eight people were killed and scores injured when a crowd surged toward a stage at a Houston music festival on Friday night, squeezing audience members who had nowhere to escape, officials said.

About 50,000 people were at the sold-out outdoor Astroworld Festival at NRG Park -- the stadium complex where the Astrodome and the NRG Stadium stand -- when the incident happened just after 9 p.m. CT, officials said.

Video from the event showed the performer on stage -- rapper and event organizer Travis Scott -- pause and look on in confusion as an ambulance with flashing lights moved into the densely packed crowd.

"The crowd for whatever reason began to push and surge towards the front of the stage, which caused the people in the front to be compressed -- they were unable to escape that situation," Houston Fire Chief Sam Peña told CNN Saturday morning.

That sparked panic, and the situation worsened and overwhelmed security personnel there, he said.

"People began to fall out, become unconscious, and it created additional panic," Peña said at a news conference.

More than 300 people were treated at a field hospital set up near the festival, Peña said.

Twenty-three people were taken to hospitals, and eight of them died, Peña said. One patient is 10 years old, and at last check was in critical condition, Peña told CNN Saturday morning.

Some of the patients were in cardiac arrest as they were taken to hospitals, Peña said. Further details about the injuries weren't immediately available. The causes of death will be determined by a medical examiner, he said.

The deadly surge came hours after at least one person was injured when people rushed through a VIP entrance to the event in the afternoon.

And it came two years after three people were trampled and injured at the same festival as many rushed to enter in 2019.

Crowd members attempt CPR on the injured

People who attended Friday's concert shared on social media the chaos that ensued after the deadly nighttime surge. Medical personnel were so overwhelmed with the injuries that some audience members attempted to administer CPR.

Houston police and event security staff stopped the concert "as soon as the situation got to the point where it was overwhelming the resources there," but by then "the damage had been done," Peña said.

Peña said the cause of the surge was not immediately clear.

Investigators will review video of the scene and look at how the venue was laid out and whether it had enough exit points, Peña said.

The investigation will explore "what caused, one, the issue of the crowd surge, and two, what prevented people from being able to escape that situation," Peña said.

In a statement on Twitter Saturday morning, festival organizers said "our hearts are with the Astroworld Festival family tonight -- especially those we lost and their loved ones," and that they "are focused on supporting local officials however we can."

Saturday's portion of the planned two-day event is canceled, organizers said.

"As authorities mentioned in their press conference earlier, they are looking into the series of cardiac arrests that took place. If you have any relevant information on this, please reach out to @houstonpolice," the tweet reads.

Astroworld organizers did not immediately respond to CNN's request for comment early Saturday morning.

Houston's emergency management office established a hot line for people who haven't been able to contact those known to have attended the concert.

People rushed through gate hours earlier -- and 3 were trampled at event two years ago

Earlier in the day, video from CNN affiliate KPRC showed numerous people rushing through a VIP entrance at the event -- knocking over metal detectors and sometimes other people, and ignoring security staff.

The video showed some people helping a few others up. Peña said he didn't know what caused that rush, either.

"We do know that we had people jump the fence," and at least one person was injured in that afternoon rush, Peña said.

In 2019, three people were trampled and hospitalized as thousands rushed to get into the festival.

CNN asked Peña whether that instance led to special precautions at this year's event. "It's obvious that if they did, they weren't enough," Peña responded.

The event, now in its third year, is organized by Scott, a Houston native. It had been scheduled to run from Friday through Saturday, according to the event's website.

The festival was slated to feature artists including SZA, Bad Bunny and 21 Savage.

Houston mayor offered condolences to the loved ones of those killed.

"Organizers held the event to bring people together for music, but it sadly ended in tragedy. Thanks to police, fire & other agencies that responded to assist," Mayor Sylvester Turner posted to Twitter.