An investigation is under way after a ceiling collapsed at the Apollo Theatre in central London injuring 76 people, including seven seriously.
Members of the audience at the packed theatre on Shaftesbury Avenue in the West End escaped covered in blood and dust after masonry fell five storeys onto their heads.
About 700 people were at a performance of The Curious Incident Of The Dog in the Night-Time on Thursday night, the BBC reports.
The London Fire Brigade said ornate plasterwork ceiling collapsed in the 112-year-old theatre bringing down part of the lighting rig about 8.15pm. Eyewitnesses heard a "crackling" noise, but thought it was part of the show.
The Apollo's owner described it as a "shocking and upsetting" incident. Police said there is no evidence that the collapse was caused by criminal activity, but are keeping an open mind.
Police and emergency crews were at the scene within minutes and rescuers commandeered three double decker buses to transport the injured. A total of 58 people were taken to hospital, but there were no life-threatening injuries.
Amy Lecoz, who attended the play with her two teenage children, said: "The entire dome roof fell down on the audience just in front of us. We were protected by the balcony above and we ran. People started screaming. We thought it was water ... We thought it was a part of the show. I grabbed my kids and ran."
Another witness said she heard a "strange crackling noise" before "the roof just crumpled". The theatre "suddenly went dark" with "dust clouds everywhere".
One woman said she initially thought it was part of the show.
"Then what we felt was a loud bang, debris falling on us," she said.
Another woman said: "We heard a creak and somebody screamed, then somebody from over there went 'look out' and then we saw part of the ceiling collapse. Within a second a massive cloud of dust filled the entire theatre."
The Apollo was built in 1901 and has 775 seats over four levels. The Curious Incident Of The Dog In The Night-Time has been running in London since August 2012. The play started at The National Theatre before transferring to the Apollo in March this year.