At least eight people have been killed and several others injured in a crowd surge during a Travis Scott concert at Astroworld Festival in Houston.
The crowd had moved closer to the stage while Scott, who runs the festival, was performing on the opening night.
The Houston Chronicle reports that the rapper stopped several times during his 75-minute set after spotting fans in distress near the front of the stage, and that he asked security to help people out of the crowd.
The local fire and rescue service took 17 people to nearby hospitals, with 11 of them in cardiac arrest, fire chief Samuel Pena said.
Mr Pena added hundreds of others were injured and the show was called off shortly after the crush occurred.
“The crowd began to compress towards the front of the stage, and that caused some panic, and it started causing some injuries,” he said, adding that people “began to fall out, become unconscious, and it created additional panic”.
There were also people treated at the scene at the NRG Park, with a field hospital set up.
Footage circulating from the event shows fans trying to get the attention of production staff and security to make them aware that something was wrong.
Chief Lt Larry Satterwhite from Houston police was near the front when the tragedy unfolded.
“It seems like it happened with just over the course of a few minutes – suddenly we had several people down on the ground experiencing some type of cardiac arrest or some type of medical episode,” he said.
“We immediately started doing CPR.”
Houston Police Chief Troy Finner has asked for calm, saying that people should not jump to conclusions as to what may have caused the crowd surge.
He said: “I think it’s very important that none of us speculate. Nobody has all the answers tonight.
“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. We don’t know, but we will find out.”
Officials did not immediately know what the cause of deaths were, nor had those who had died been identified.
A reunion centre has been set up for family members who were unable to reach relatives who were at the event.
A crowd of 50,000 people showed up for the two-day festival in Texas, which featured artists such as SZA, Tame Impala and Earth, Wind & Fire.
The second day has now been cancelled.