An investigation is under way today to try to find out why the ceiling collapsed at the Apollo theatre in the West End on Thursday night, injuring at least 79 people.

A large section of plaster fell on to the audience during a production of The Curious Incident Of The Dog In The Night-Time. Emergency Services were called to the Grade II listed theatre in Shaftesbury Avenue at 8.10pm and witnesses reported seeing theatre goers leaving in tears and some covered in blood. Seven people are said to have been seriously injured.

Graham Ellis, deputy assistant commissioner of the London Fire Brigade, told the BBC that plasterwork had fallen on to the upper circle, the dress circle and the stalls.

Around 720 people had been watching the performance at the time of the collapse.

The London Ambulance Service sent 29 ambulance crews to the scene plus seven responders in cars or on motorbikes and a hazardous area response team.

They treated 79 patients and took 56 to hospital - 47 with minor injuries and nine had suffered more serious injuries including head and back injuries.

Among the vehicles used to transport patients with minor injuries were two London buses.

Incident Commander Maria Smith, who was one of the first on scene, said: “When I arrived it was dark and extremely dusty and people were lying on the floor of the theatre. We very quickly set up a casualty clearing area in the foyer of the theatre and the walking wounded were assessed and treated there for injuries such as cuts and grazes, breathing problems and head injuries.

“All the staff involved did an excellent job to help ensure that people received medical attention and those who needed further treatment were taken to hospital.”