Hundreds of theatregoers were evacuated after the ceiling of a packed London theatre collapsed midway through the evening performance on Thursday.
At least 700 people were evacuated from the Apollo Theatre, in Shaftesbury Avenue, police confirmed.
A rescue operation began at 8.15pm following the incident. Eighty eight people were reported to have been injured, seven of them seriously.
Police said they were not aware of any fatalities.
Witnesses reported seeing members of the audience trapped, bleeding and with broken bones.
The interior of the Grade II-listed building was left obscured by a cloud of dust and debris during the performance of The Curious Incident Of The Dog In The Night-Time.
Actors were seen to interrupt their performance to point at the ceiling. Witnesses said they initially thought it was part of the show, before "seeing the look on the ushers' faces" and fleeing the sold-out performance.
Some of the casualties were seen being carried out on stretchers. Witnesses reported seeing other people being treated for broken bones, and wearing oxygen masks.
Khalil Anjarwalla, who was watching the play with his heavily pregnant wife and her parents, said people were screaming and rushing for the exit as the roof collapsed on to the stalls.
He said: "We were watching the play and saw some movement above us but we didn't know whether it was part of the play.
"Within an instant the entire roof caved in and you couldn't see the sky, but at least the first layer of the roof was entirely gone and then dust filled the entire theatre. Everyone was just screaming and people were rushing for the exit, clambering over chairs. It was completely horrific. We had to get out, calmly. I remember thinking the cloud, the dust - it reminded me of those scenes from 9/11 in the aftermath of the building collapsing."
One male cast member said: "People are in there, people are hurt. We don't know what happened to them."
One member of the audience, who gave his name only as Steve, said he was on the balcony when there was a "massive crash", with plaster "smashing down" on the stall below. "What it was like for the people down below, I can only imagine," he said.
An emergency centre was set up in the Gielgud Theatre next door to treat the walking wounded, after members of the audience were seen "pulling people out" from underneath debris.
Audience member Hannah George, 29, said a part of the ceiling several metres square had fallen in front of her eyes.
"Everyone moved very quickly to the door but it wasn't every man for himself," she said.
"People were helping others, ushers were holding open the doors. "From down below, you could hear screams from the stalls."
One of the actresses said: "Part of the ceiling collapsed. I don't know what happened to the people underneath, but it will be a small miracle if people aren't hurt badly."
Jess Bowie, the content editor of The House magazine, tweeted: "Don't know if anyone is trapped in there but people outside are covered in dust and some in blood. Utterly horrible." The cast manager for the play said the cast were uninjured. The Curious Incident Of The Dog In The Night-Time, has been running in London since August 2012.
Winner of a record-breaking seven Olivier Awards - including Best Play - the show started at The National Theatre, before transferring to the Apollo in March.
The production is based on Mark Haddon's award-winning novel.
the Apollo was designed by architect Lewin Sharp for owner Henry Lowenfield, and completed in February 1901.
Nica Burns and Max Weitzenhoffer bought it with several others in 2005, creating Nimax Theatres, which still owns the Apollo.