The ceiling of the Apollo Theatre in London collapsed during a performance that drew a full audience. Metropolitan police said that there are casualties.

According to The BBC, the collapse happened late Thursday night local time, as The Curious Incident Of The Dog in the Night-time show was onstage. An eyewitness reported hearing "a crackling” noise and another said that the “entire dome roof” collapsed.

CNN reports that police responded at 8:15 p.m. and issued a tweet, noting that, “We are aware of a number of casualties but we have no further detail at this early stage.”

Amy Lecoz, who was in the theater with her two children, told the BBC that they were “protected by the balcony above and we ran” and that others started screaming.

Another eyewitness said that some people thought it was part of the show, but then the ceiling came down. “There was dust everywhere, everybody's covered in dust. We got out fairly quickly, I think everyone was quite panicked,” the man said.

“Absolutely petrifying,” witness Jess Bowie tweeted, the BBC reports. “People outside are covered in dust and some in blood. Utterly horrible.”

The Apollo Theatre was built in 1901 and is currently owned by Nimax Theatres. There are 775 seats and four levels.