At least 88 people were injured, seven of them seriously, when the ceiling of a London theatre collapsed late Thursday, bringing down parts of balconies with it, police said, dpa reported.
Witnesses described scenes of chaos and panic as masonry began falling and the theatre filled with dust, but said the evacuation of the building had been orderly.
Police confirmed that they were called to the historic Apollo theatre in London's West End at 8:15 pm (2015 GMT). Around 720 people were inside watching a performance of The Curious Incident Of The Dog In The Night-time.
"We were in the balcony, about five rows from the front, and we saw a few people in the front of the balcony row get up and start moving towards the right," 29-year-old Hannah George said.
"Very quickly, the second and third rows started moving all together. We wondered if this was part of the show. Then I heard someone scream, and you heard a shriek - then a chunk of the ceiling collapsed."
She said the ceiling "must have hit people down below."
"Very quickly ushers held the doors open. It wasn't every man for himself. It was very ordered," George said.
"There were people in front going, 'You OK?' and trying to get people out. There were people coming out who were more seriously injured. There were loads of people coming out shaking, and a fellow next to me had quite a badly bleeding arm and a ripped shirt."
All those who were trapped had been rescued, said fire brigade spokesman Nick Harding, who was at the scene. Specialist urban search and rescue advisors had offered structural guidance to the theatre, he said.
"In my time as a fire officer, I've never seen an incident like this," Harding said.
A spokesman for Nimax Theatres, which owns the Apollo, said the ceiling collapse was a "shocking and upsetting incident," with an investigation underway into the cause.
Police said there was no suggestion of a "criminal act," but that they were keeping an "open mind".
Theatre-goer Khalil Anjarwalla, who was there with his wife, who is in advanced pregnancy, said he had seen some people "quite badly" cut.
"I was in the upper circle with my family when, about 45 minutes in, people started shouting and screaming," he said. "We thought it was part of the play. But the ceiling was crumbling. Within an instant the whole roof seemed to come down."
His wife, Aliya, said: "The actors just seemed to run from the stage. They had obviously seen what had happened."
Andrew Howard-Smith said that people leaning on the balcony had caused the front 60 centimetres to break off.
"I saw the edge of the balcony come down - that's what I saw. We were on the balcony below," he said. "In the production you had to hold on to the rail and lean over to see what was going on, and we were doing the same."
"Everybody must have got hold of the brass rail and just pushed it over, and then the edge came off. That was the only bit that came off, just the edge."
The streets outside were filled with dust-covered theatre-goers, many of them bleeding, witnesses said.