Parts of the ceiling at the Apollo Theatre in central London collapsed during a packed performance on Thursday night, leaving some 76 people injured, several of them seriously, officials said.

At the scene of London Apollo theatre roof collapse

The incident happened at during the West End show "The Curious Incident of the Dog in the Night-time" and comes the week before Christmas when London's theatres are traditionally busy.

Witnesses heard creaking noises in the 112-year-old theatre before the collapse but thought it was part of the show, before a section of the ceiling collapsed and brought down parts of the balconies.

Police said they weren’t aware of any fatalities “at this early stage,” following the incident at 8.15 pm local time, but said that seven seriously injured people had been taken to hospital.

More than 50 “walking wounded” were being treated at a nearby theatre, police added.There were around 720 people in the audience at the time, the London Fire Brigade said.

Pictures on social media showed people fleeing the theatre with head injuries and covered in dust.

Martin Bostock was in the audience with his family, and said “complete chaos” erupted in the theatre. “At first we thought it was part of the show,” he told Sky News. “Then I got hit on the head. “

There were unconfirmed reports that part of the balcony had collapsed on members of the audience below.

Spectator Desmond Thomas, 18, part of a school party watching the show, said they heard noises before the accident.

"Maybe 10 minutes into the performance we heard a tap-tap noise, we thought it was rain," he told AFP.

"There was a crack and then it suddenly seemed to get bigger and suddenly it collapsed. The next thing we knew the whole theatre filled with dust and smoke."

A thunderstorm had hit London in the hour before the incident.