Videos posted on social media showed concertgoers running and screaming, and there were unconfirmed reports of explosions.
LONDON — The sound of explosions thundered through a concert arena in Manchester, England, on Monday night just as a performance by the pop star Ariana Grande was ending. The police reported multiple deaths and injuries as the panicky crowd of spectators, which included children, fled.
There was no immediate word from the police on the cause, but it immediately evoked the terrorist attacks in Paris in November of 2015, which included a deadly assault inside a concert arena where the Eagles of Death Metal had been playing.
People at the concert at the Manchester Arena said they heard what sounded like explosions at the end of the show.
One concertgoer, Sasina Akhtar, told The Manchester Evening News that there had been an explosion at the back of the arena after the last song. “We saw young girls with blood on them, everyone was screaming and people were running, ” she said.
Ariana Grande, a 23-year-old singer with a big voice who started her career as a star on a Nickelodeon TV series, is on an international tour supporting her 2016 album, “Dangerous Woman.”
The tour was scheduled to continue on Thursday at the O2 Arena in London. Two additional acts, Victoria Monét and Bia, performed as openers.
”Ariana is O. K., ” said her publicist, Joseph Carozza. “We are further investigating what happened.”
The authorities had cordoned off the area around the arena early Tuesday, and a helicopter was flying overhead.
The BBC interviewed one witness, who was waiting outside the Manchester Arena to pick up his wife and daughter, recounting that the “whole building shook, ” that there was “carnage everywhere, ” and that the explosion appeared to come near the stadium’s ticket area. But the BBC emphasized that it was not clear what caused the explosion.
Videos posted on Twitter showed concertgoers running and screaming from their seats. Hannah Dane, who attended the performance, told The Guardian that she had heard “quite a loud explosion heard from inside the Manchester Arena.”
She added, “It shook, then everyone screamed and tried to get out”.
The explosion occurred around 10: 45 p.m., just as the concert was ending.
“There are a number of confirmed fatalities and others injured, ” the Greater Manchester Police said in a statement.
The Manchester Arena, opened in 1995, can hold up to 21,000 spectators; it was not clear how many people were in the crowd for the concert.
The stadium is next to a train terminus, Victoria Station, which was evacuated .
Karen Ford, a witness, told the BBC that she was leaving the concert when “everyone was just getting out of their seats and walking toward the stairs when all of a sudden a huge sound, which sounded like an explosion, went off.”
“Everyone tried to push people up the stairs, ” she recalled, adding that in the chaos, people tried to push past a woman in a wheelchair as children screamed.
She said there was no smoke, just one very loud bang. “It was very, very loud.” She said her husband thought he had heard a second explosion.”there were shoes on the floor, ” left behind by people who had fled, she recalled.
“Just chaos, ” she said. “I was trying to tell people to calm down.” She added that the crush of people trying to flee created a perilous situation: “We were being crushed.”
Outside, Ms. Ford said, parents awaited their children who were attending the concert, checking their smartphones in a panic. “Everyone was trying to find each other.”
