LONDON: Investigators were seeking Friday to establish why the ceiling of a packed London theatre collapsed, injuring 76 people and coating terrified audience members with rubble.
A sell-out crowd of around 720 people was in the Apollo Theatre in Soho on Thursday night when ornate masonry and rigging fell some five storeys onto their heads.
Witnesses said they heard creaking noises in the 112-year-old theatre but thought it was part of the show they were watching, "The Curious Incident of the Dog in the Night-time".
Then debris and dust filled the air, sending coughing, terrified theatregoers -- many of them families enjoying a pre-Christmas treat -- fleeing for the exits.
Rescuers commandeered three iconic red London double-decker buses to transport the wounded, while the city's normally tourist-thronged "Theatreland" was brought to a stunned halt.
Ambulance staff treated 76 patients, taking 58 to hospital, where seven were described as having serious but not life-threatening injuries.
A surveyor examined the theatre overnight and said the roof was secure, but investigations are now being carried out by the local authority to establish what happened.
The abnormally heavy rain that fell in the hour before the ceiling collapsed shortly after 8:00 pm (2000 GMT) is likely to be one line of inquiry.
"We will not know the cause of the incident until all investigations have been completed but checks are ongoing," said Councillor Nickie Aiken of Westminster Council.
"This appears to be an isolated incident, but we will continue to work with theatres throughout the day to ensure that all safety precautions are in place."
All historic theatres are required to undergo rigorous safety checks on their roofs every three years, she added.
Witnesses told of terror inside the Edwardian-era theatre, which has three tiers of balconies, the uppermost of which is said to be the steepest in London.
"A section of the theatre's ceiling collapsed onto the audience who were watching the show. The ceiling took parts of the balconies down with it," senior firefighter Nick Harding told reporters.
"In my time as a fire officer I've never seen an incident like this."
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."
Simon Usborne, a journalist for The Independent newspaper who was watching the show, said there was "chaos".
"Loud bangs, cracks. Thought was part of show then whole interior of theatre filled with curtain of dark grey dust and debris, falling on heads of anyone not sheltered," he tweeted afterwards.
"People emerging soon after bloodied -- children crying -- family show -- people dumbfounded."
Prime Minister David Cameron said he was being kept updated on the incident and was "grateful for the fast work of the emergency services in helping the injured".
Some of the injured were treated in triage centres set up in the lobbies of the nearby Gielgud and Queen's theatres.
"In the finest traditions of Theatreland, they very quickly rallied around," said fire brigade spokesman Graham Ellis.
He said that "heavy ornate plaster" had fallen from the roof onto theatregoers in the circle, dress circle and stalls.
Audience member James Kearney, who was given a ticket to the show as a present, told AFP there were "people with blood on their heads in shock" behind them.
Kearney's companion Dee Stephenson said there was so much dust afterwards they had to feel their way out.
"Everybody was in a trance-like state. A lot of people were in absolute shock," Stephenson told AFP. "We were extremely fortunate."
Based on an award-winning novel by Mark Haddon, "The Curious Incident of the Dog in the Night-time" has been running in London since August 2012.
Haddon said on Twitter that the incident was "horrifying" and that he was "hugely relieved that no one died".
The owner of the Apollo, Nimax Theatres, said the ceiling collapse was a "shocking and upsetting incident".