Seven of those suffered serious injuries when part of the roof caved-in at the Apollo Theatre during a packed performance of the Curious Incident Of The Dog in the Night-Time.
Eight fire engines and more than 50 firefighters were called to the scene at 8.15 on Thursday night when a large section of ornate plaster work fell onto the audience.
Kingsland Station Manager Nick Harding said: “We believe around 720 people were in the theatre at the time. A section of the theatre’s ceiling collapsed onto the audience who were watching the show. The ceiling took parts of the balconies down with it.
“Firefighters worked really hard in very difficult conditions and I’d like to pay tribute to them. They rescued people from the theatre, made the area safe and then helped ambulance crews with the injured.
“Specialist urban search and rescue crews were also called to the scene to make sure no one was trapped. Fortunately all those who were trapped have been rescued and treated for injuries or taken to hospital.
“In my time as a fire officer I’ve never seen an incident like this.
“I imagine lots of people were out enjoying the show in the run-up to Christmas. My thoughts go out to all those affected.”