At least ten people were injured when the stage collapsed at a Sound of Music tribute show at Birmingham's Alexandra Theatre last night.
Dozens of people dressed as nuns were on the stage as part of the Sing-a-long Sound of Music show when it gave way, plunging them 20ft.
Firemen using ladders and stretcherboards rescued the injured while the 1,300-strong audience, many in fancy dress, were evacuated and the sell outperformance abandoned.
Doctors and nurses from the audience tended to some of the walking wounded before paramedics and ambulance crews started ferrying the more serious cases to hospital.
At one point, while the injured were still being rescued or tended to, an announcement was made stating the show would continue after 15 minutes.
That was greeted with booing and jeers from the audience and after about ten minutes they were told the show was off and tickets would be refunded.
Police initially said up to 20 people had been injured, including three seriously, and were were taken to three hospitals.
However, West Midlands Ambulance later said the number of casualties was ten, none thought to be serious.
The accident happened just after 8pm during the warm-up routine to the show which encourages people to dress as members of the Von Trapp Family singers made famous in the Julie Andrews film.
About 30 people, all dressed as nuns, were called on to the stage to take part in a fancy dress competition when a rumbling sound was heard in the stalls. A temporary section of stage, which covered the orchestra pit, gave way and the revellers fell in.
One audience member, Hazel Jones, from Solihull, said: 'I just couldn't believe it. We were having a great time, and lots of people had gone on to the stage. 'The metal struts held up part of the stage and they must have given way. There was a noise, then suddenly a huge crash, the people disappeared down this big hole. It was such a distance for them to fall.'
After the accident the compere came on stage and was booed after asking the audience if they wanted the show to continue.
Shirley McDonald, from Lichfield, said: 'People went down to the front and started trying to help. They were picking up big pieces of wood from people.
'Everybody booed, they couldn't believe it. But the compere said 'I am only telling you what I've been asked to tell you'.'
Ross Halifax, from Lichfield, said: 'Everyone was really happy and jolly and having a good time, but then nuns at the front disappeared completely. At first we thought it might be part of the show but soon realised it wasn't.'
Martin Ronan, the promoter of the show, described the accident as a tragedy.
He said: 'People went on to the stage and the front part of it collapsed. We have been running the show for five years and we have never had anything like this before.
'It's a terrible shock to me, it's a complete tragedy and I don't know why it's happened.' Leigh Barrett, spokesman for Clear Channel Entertainment, which owns the theatre, promised a full investigation.
She said: 'Nothing like this has ever happened at the Alexandra before, and there will be an extremely thorough investigation.
'Although it's too early to say if it will be open tomorrow, that is unlikely.'
A spokesman for the Health and Safety Executive said it had been alerted by the police.
But an investigation into the circumstances of the accident was the responsibility of the local authority until it approached the HSE for expert assistance, the spokesman said.