A free concert in Las Vegas erupted into mayhem over the weekend when the heat sparked a mass wave of fainting and vomiting.

Unlucky concertgoers who were attending band Sleeping With Sirens’ gig on Saturday in Sin City were packed like sardines into the Fremont Street venue to watch the rockers belt out some of their best known songs.

As the show began, temperatures had already soared above 40C, with the cramped conditions and lack of water available to those trapped in the middle sparking chaos.

As a result, things became too much for many in the audience, and panic quickly set in as concertgoers realised they were trapped and unable to free themselves.

One fan claimed that people were “dropping like flies” to the floor in front of her.

“I don’t think they were equipped for the crowd that was going to be there, and by the time they realised it, it was too late,” a concertgoer told KLAS News. “It was getting worse and worse. It was so bad, people were standing in the middle of the metal detectors.”

“People were just dropping like flies right in front of me.”

Another told the station that people were “passing out” next to them and that they themselves soon began to “feel the crunch”.

“We stayed for about three and a half, four songs, and we just started getting crunched more and more,” she explained.

She said their excitement quickly turned into concern: “There were people passing out next to us, behind us, everywhere.”

The venue – which is a pedestrian mall that doubles as an open-air entertainment district – told KLAS News in a statement that they had expected guests to bring their own water bottles to the event.

“Guests attending Fremont Street Experience Special Events are welcome to bring sealed, plastic bottles into the concert area. For the safety and enjoyment of all guests, glass containers, aluminium cans and metal bottles are not permitted. We appreciate everyone’s co-operation in helping us provide a safe and enjoyable experience at Fremont Street Experience.”

Meanwhile, last year a Netflix documentary shone a spotlight on the doomed 2021 Travis Scott concert Astroworld that turned a celebration into a deathtrap.

At the peak of Scott’s performance that night, a sea of 50,000 crowdgoers swelled to the stage.

The horror human crush squeezed 10 people to death. Dozens more were injured. It was among the worst concert tragedies in US history.