Stephen Fry is among the theatre stars who have told of their shock after the ceiling of the Apollo theatre in London collapsed.
More than 80 people were injured, seven seriously, when the ceiling collapsed on top of them during a performance of The Curious Incident Of The Dog In The Night-time.
Many were described as "walking wounded" after plaster from the Grade II listed theatre in London's West End plummeted into the stalls below, dragging a section of the balcony with it, striking members of the packed audience and filling the theatre with clouds of thick dust.
Stephen, who has previously appeared at the Apollo, tweeted: "Lots of love from @ShakespeareBway to all at our old friends at the #ApolloTheatre - do hope no one is too hurt. What a terrible shock."
Actress Sheridan Smith said: "Terrifying, hope everyone's OK..."
Surveyors have now said the ceiling of the Apollo is "sound".
The cause of the accident is being investigated and Westminster City Council is expected to report on a structural assessment of the Shaftesbury Avenue venue this afternoon.
Westminster Council's cabinet member for community protection, Nicola Aiken, told the BBC Radio 4 Today programme: "District surveyors have attended and declared that the ceiling structure is sound and only plaster fell. Today we are waiting for the police to hand over the theatre to us as we are the health and safety authority for historic theatres in Westminster and we will be doing checks of all historic theatres' consents and licensing today in liaison with the Society of London Theatres because we want to reassure theatre-goers that theatres are safe to attend.
"We will be carrying out the investigation as to why the accident happened in the first place, but that will take some time."
One line of inquiry will be the effect of adverse weather on the 100-year-old building.
Forecasters confirmed there was an abnormally high concentration of rain, hail and lightning strikes in London between 7pm and 9pm last night, with nearly 15 per cent (14.5 per cent) of the average monthly rainfall for one area in December falling in one hour.
London Mayor Boris Johnson said the response of the emergency services had been "exemplary" and that the West End remained "open for business".
Ms Aiken also said: "Our teams have been on site at the Apollo Theatre last night and again this morning and will remain on site until all checks are complete. As the investigation is ongoing, we are unable to comment further on specifics.
"However, we can say that the Apollo's health and safety checks are up to date.
"Each historic theatre is unique and we have no reason to believe this is other than an isolated incident. We have confirmed today with the Society of London Theatre that all theatres' safety checks are up to date; however, as a precaution, all historic theatres are carrying out further safety checks today."
Ms Aiken refused to comment on suggestions that extreme weather may have caused the ceiling collapse, adding that officers would leave "no stone unturned" in investigating the cause.
More than 700 people were inside the Apollo - which was 45 minutes into the National Theatre's performance - when members of the audience started screaming as it appeared parts of the ceiling caved in.
Police commandeered three London buses to take the injured to hospital, many of whom were left bloodied and bandaged, and a makeshift triage was set up at the Gielgud Theatre.
London Ambulance Service said it treated 76 patients, of whom 58 were taken to four hospitals. Of those, 51 had suffered minor injuries and seven more serious injuries. There were no fatalities.
Audience members spoke of hearing a loud "creaking" which some initially thought was part of the show. Theatre-goer Khalil Anjarwalla said he, his heavily pregnant wife and her parents managed to escape from the theatre safely after "kilos of concrete plummeted from the ceiling".
Business owner Mr Anjarwalla, 29, said: "I was in the upper circle with my family when, about 45 minutes in, people started shouting and screaming. Within an instant the whole roof seemed to come down. We saw a lot of people completely covered in dust - I could hardly breathe. We had to get out, calmly. I remember thinking the cloud, the dust."
Photographs from inside the theatre showed heavy beams and wood strewn across seats, which were coated in debris and dust.
Sean Walsh, who was visiting the show with his girlfriend, said they were sitting in the balcony when they first spotted a group of people below them shouting to leave the theatre immediately. Mr Walsh, 41, from north London, said: "We were right up in the gods and a couple in the group below just said 'Go!' We thought they were just leaving because maybe they were bored, and my girlfriend thought maybe they had seen a mouse. But then the whole of the ceiling just came down."
A spokeswoman for Nimax Theatres, which owns the Apollo, said performances had been cancelled until Saturday January 4.