The deadly explosion that rang out during an Ariana Grande concert Monday night in the northern United Kingdom triggered a “chaotic” scene, witnesses said in the immediate aftermath, with one adding: “It was a huge explosion -- you could feel it in your chest.”

Police said several people died. Investigators urged people to avoid the area around the Manchester Arena as they looked into the cause.

“It happened just in front of us at the top of the stairs. We didn’t know what had happened. It could have been a gun or a bang or an explosion,” 17-year-old Courtney Spencer, a college student who went to the concert with a friend, told The Sun. “We just grabbed each other and got away.”

“Everybody was screaming,” Catherine Macfarlane, who escaped the blast, told Reuters. "Running and screaming and just trying to get out."

A 'NUMBER OF CONFIRMED FATALITIES,' POLICE SAY

"There was a gentleman on the floor with his leg all bleeding and woman with blood down one side of her face,” said a bartender who gave only his first name, Tyler, Sky News reported.

Video from inside the arena showed concertgoers screaming as they made their way out amid a sea of pink balloons. Joseph Carozza, a representative from Grande's U.S. record label, said the singer was OK.

"It's a lot of teenagers - they're all in tears," Tyler continued. "One girl had a panic attack and another had streaming tears, a woman had a heart attack just outside.”

CELEBRITIES RESPOND TO REPORTS OF EXPLOSION

"It was one bang and essentially everyone from the other side of the arena where the bang was heard from suddenly came running towards us as they were trying to exit," concertgoer Majid Khan, 22, told Britain's Press Association.

"The bang echoed around the foyer of the arena and people started to run," 17-year-old Oliver Jones added.

The Associated Press contributed to this report.