London's Apollo Theatre balcony collapse during performance Police called to Grade II listed theatre in London's West End at 8.15pm The Curious Incident Of The Dog In The Night-time was being performed Part of the balcony started creaking before section of theatre collapsed Theatre-goers left crying and bleeding - and up to 80 people are injured By Mark Duell and Damien Gayle Dozens of theatre-goers were injured tonight in chaotic scenes described as 'like an avalanche' when part of a balcony collapsed during a performance at a major West End theatre. Seven people were seriously injured and there were 81 walking wounded following the incident which happened at around 8.15pm inside the Apollo Theatre in Central London. Masonry from the Grade II-listed theatre on Shaftesbury Avenue plummeted into the stalls below, striking members of the packed audience and filling the theatre with clouds of thick dust. Helping hand: A bandaged man comforts a woman following the collapse at the Apollo Theatre Injuries: A woman stands bandaged and wearing a blanket from the emergency services in Central London Keeping warm: A man wraps himself in an emergency blanket provided by rescue services after the incident Makeshift ambulanc: Shocked and injured theatergoers are transported to hospital in a commandeered London bus following an incident during a performance at the Apollo Theatre A capacity audience of more than 700 people was inside the theatre, which was 45 minutes into the National Theatre's performance of The Curious Incident Of The Dog In The Night-time. Audience members then started screaming as parts of the ceiling appeared to cave in, with some eyewitnesses 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 said: "I was in the upper circle with my family when, about 45 minutes in, people started shouting and screaming. We thought it was part of the play. But the ceiling was crumbling. Within an instant the whole roof seemed to come down. We saw a lot of people completely covered in dust - I could hardly breathe. Horror: Halfway through the first half of the performance, part of the balcony started creaking before a section of the theatre collapsed Inside the theatre: London Fire Brigade confirmed that eight fire engines had been sent to the scene Running to help: One man, who was in the audience at the Grade II listed theatre with his family, said he suffered a head injury after he was hit by falling debris We had to get out, calmly. I remember thinking the cloud, the dust - it reminded me of those scenes from 9/11 in the aftermath of the building collapsing. There was a lot of crashing noise and part of the roof caved in. There was dust everywhere, everybody's covered in dust' Ben, eyewitness The 29-year-old, who is from Nairobi in Kenya, said: "I was very close to the Westgate Mall which was the scene of the recent terror attack. So my first thought was instantly to check whether we should be ducking for safety. We then realised it was a structural issue and tried to get out. Mr Anjarwalla, who was visiting his in-laws with his English wife, Aliya, said: "The actors just seemed to run from the stage. They had obviously seen what had happened. We initially thought it was part of the show. Thankfully we are all OK. My wife is seven months pregnant but she is OK. We feel very blessed. He said some people seemed to be "cut quite badly." Discussions: Rescue services at the scene of an apparent balcony collapse at the Apollo Theatre in London Discussions; Firemen confer at the scene after the incident at the Apollo Theatre on Shaftesbury Avenue Emergency response: The London Fire Brigade said the theatre was almost full, with 'around 700 people' watching the performance On location: Walking wounded were taken from the scene in ambulances as a team of firefighters rushed through the front stage door in Archer Street Police said a London bus was used to take the casualties to hospital, while members of the public were asked to avoid the area. Emergency services were called to the scene shortly after 8.15pm, as eyewitnesses reported many theatre-goers crying and trying to make contact with family members as some were initially thought to be trapped inside the building. The first London theatre of the Edwardian era, the doors of the Apollo Theatre first opened on February 21, 1901, for the American musical comedy The Belle Of Bohemia. The three-galleried auditorium, which seats 796, is decorated with elaborate plasterwork and the balcony on its third tier is considered the steepest in London. Designed by architect Lewin Sharp, the building boasts elaborate sculpted work on the stone fascia to the front. To neighbouring streets the building is of plain brick. It is one of four London playhouses owned by Nimax Theatres, a group owned and operated by Nica Burns and Weitzenhoffer. Others include the Garrick Theatre, the Duchess Theatre and the Lyric Theatre. All were previously owned by Andrew Lloyd Webber. Jess Bowie, content editor of The House magazine, tweeted: "Was just seeing 'The Curious Incident' in the West End when the roof of the Apollo Theatre caved in. Absolutely petrifying. Don't know if anyone is trapped in there but people outside are covered in dust and some in blood. Utterly horrible. Andrew Howard-Smith, 68, said: "I saw the edge of the balcony come down, that's what I saw. We were on the balcony below. In the production you had to hold on to the rail and lean over to see what was going on, and we were doing the same. Everybody must have got hold of the brass rail and just pushed it over, and then the edge came off. That was the only bit that came off, just the edge. It wasn't the whole of the balcony, just the front 2ft. Libby Grundy, 65, said: "There was a bang, and then a huge cloud of dust. At first I thought it was a special effect. "I heard somebody on the stage say "Oh bloody hell," because they must have seen it. And then people realised it must be some sort of emergency and people started getting up. People didn't panic. People were quite shaky when they got out. There wasn't any screaming. People were scared, but they weren't screaming. I feel quite shaky now. Young and old: A girl wraps herself in a blanket provided by rescue services following the incident Carried away: A woman lies on a stretcher surrounded by rescue workers, awaiting evacuation Paramedics helping: An injured woman is moved on a stretcher following an incident at the Apollo Theatre Scary: Many theatre-goers were crying and trying to make contact with family members as some were still trapped inside the building One 29-year-old, who would only give his name as Ben, said: "It was about halfway through the first half of the show and there was a lot of creaking. We thought it was part of the scene, it was a seaside scene, but then there was a lot of crashing noise and part of the roof caved in. There was dust everywhere, everybody's covered in dust. There was panic, there was screaming Simon Usborne, eyewitness We got out fairly quickly, I think everyone was quite panicked. 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. Trapped: A rescue operation is under way after part of a balcony in the Apollo Theatre (file picture) in Central London is thought to have collapsed during a performance Theatre: The three-galleried auditorium, which seats 796, is decorated with elaborate plasterwork and the balcony on its third tier is considered the steepest in London (file picture) He said people in the balcony filed out of the theatre calmly, but added: "It was difficult - you could hardly see the seat in front of you, due to the dust." There was a bang, and then a huge cloud of dust. At first I thought it was a special effect Libby Grundy, eyewitness The London Fire Brigade said the theatre was almost full, with "around 700 people" watching the performance. A spokesman added: "It's thought between 20 and 40 people were injured." A district surveyor from Westminster City Council was on the way to the scene to carry out structural assessment of the building. It is thought the engineer, who will be accompanied by police officers, will spend most of the night getting access inside the theatre to ensure it is safe. Council leader Philippa Roe said: "We are obviously shocked to hear the news and our immediate concerns are with the people that have been injured. Our officers are on site and they will help emergency services wherever they can. London Fire Brigade described 81 people as "walking wounded" with seven taken to hospital with "more serious injuries." Labour leader Ed Miliband later tweeted: "Sorry to hear of events at Apollo Theatre. All of our thoughts with those injured and emergency services. And a spokesman for London Mayor Boris Johnson said: "He has spoken to the Met Police Commissioner and is liaising with the relevant agencies. His thoughts and prayers are with those involved in what is clearly a very serious incident. The cast of the play includes the likes of Jo Dockery, sister of Downton Abbey's Michelle Dockery, former EastEnders actress Amanda Drew and Trevor Fox from 2000 film Billy Elliot. Winner of a record-breaking seven Olivier Awards this year - including Best Play - The Curious Incident of the Dog in the Night-time is one of the West End's hottest tickets this Christmas. Simon Stephens's adaptation of Mark Haddon's award-winning novel, directed by Marianne Elliott for the National Theatre, was already a sell-our production for the South Bank's Cottesloe Theatre before its transfer to the Apollo. The story follows Christopher, a 15-year-old boy who describes himself as 'a mathematician with some behavioural difficulties' living in Swindon. High demand: Winner of a record-breaking seven Olivier Awards this year - including Best Play - The Curious Incident of the Dog in the Night-time is one of the West End's hottest tickets this Christmas There is some suggestion, never made explicit in the story itself, that he is affected by Asperger syndrome or some other kind of high-functioning autism. It begins at seven minutes after midnight with Christopher standing beside a neighbour's dog, which has been speared with a garden fork. He is suspected of carrying out the killing, spurring him to undertake his own investigation into who murdered the animal, with each fact painstakingly recorded in a book he is writing. With an extraordinary mathematical brain that is nevertheless ill-equipped to interpret everyday life, Christopher had never even ventured alone beyond the end of his road. But, as the National Theatre puts it, 'his detective work, forbidden by his father, takes him on a frightening journey that upturns his world.' Haddon's original book, published in 2003, was the winner of more than 17 literary awards coming from as far afield as Japan, Holland and Italy, as well as the 2004 Whitbread Book of the Year Award in the UK.