LONDON -- An industry group sought to reassure theatergoers Friday that London's elegant but aging venues are safe after chunks of ornamental plaster fell from a ceiling of the Apollo Theatre, showering patrons with dust and debris and injuring 79 people.
One line of inquiry for investigators is whether a brief but intense rainstorm was a factor in Thursday's accident at the century-old building.
The Society of London Theatre said all theaters undergo "rigorous safety checks and inspections by independent experts, and incidents like last night are extremely rare."
"Our theaters entertain over 32,000 people in central London every night and all theaters take the safety of their audience, performers and staff very seriously," it said.
Witnesses have described chaos and panic as large chunks of plaster, wooden beams and dust rained down on the audience 45 minutes into a performance of "The Curious Incident of the Dog in the Nighttime."
"I thought, maybe this is part of the play," said Scott Daniels, an American tourist from the Dallas area. "All of a sudden, plaster starts raining down, huge hunks of plaster ... The lights went out and everything filled with dust -- everybody was coughing and choking."
London Ambulance Service said Friday that it had treated 79 people, 56 of whom were taken to local hospitals in ambulances and two commandeered London buses. Of these, 47 were "walking wounded" with minor injuries, while nine "had suffered more serious injuries including head and back injuries."
Nimax Theatres, which owns the Apollo, described the incident as "shocking and upsetting."
Like many of London's West End theaters, the Apollo is more than a century old, built in 1901.
The Theatres Trust, which helps preserve Britain's historic playhouses, said theater plasterwork was inspected regularly and certified by independent experts.
Westminster Council, the local authority, said an investigation was under way and an initial structural assessment had found the building is secure.
The building remained cordoned off to the public Friday. The Society of London Theatre said performances of "Curious Incident" on Friday and Saturday had been canceled.
Marc Sinden, director of the documentary series "Great West End Theatres," said that despite the accident, London's theaters are extremely safe.
"These theaters have been around for a very long time, but they are looked after and regularly maintained. They are looked after daily," he said.