Several people were injured when parts of a ceiling collapsed during a Piccadilly Theatre show in London's West End.
The venue in Denman Street was packed on Wednesday for a performance of the Arthur Miller play Death of a Salesman, starring US actor Wendell Pierce.
Audience members "heard dripping sounds indicating water was coming through the ceiling," according to the theatre production company.
More than 1,000 people were evacuated.
Four people were taken to hospital after three men and two women were treated at the scene by paramedics.
"We are ascertaining the extent of the situation, and will be providing an update on future performances as soon as possible," the Ambassador Theatre Group said.
The production team said three special performances of the play would take place at the Young Vic theatre on Friday night, as well as a matinee and evening performance on Saturday.
The performances at the Piccadilly Theatre for the rest of the week have been cancelled.
Wendell Pierce, who plays Willy Loman in the show which opened on Monday, said: "First, I hope those injured last night are recovered and healing.
"Their well-being is the most important thing. I am also so grateful that the Death of a Salesman company is able to continue performances of Arthur Miller's great play.
"The nightly audience response has been overwhelming, and I would like to thank the Young Vic for enabling us to continue on this special journey.
"In the time-honoured tradition of the theatre, the show must go on."
He apologised for having to stop the performance and evacuate the theatre.
A video shared on social media shows the US actor outside the venue asking the crowd to come back and see the play another time.
"We're so honoured that you came tonight. We are so sorry that this happened," he said.
Ticket holders for the cancelled performances will be contacted to make arrangements for the performances at the Young Vic.
BBC journalist Iain Haddow, who was in the audience, said the collapse happened about 20 minutes into the show.
He said that before the ceiling caved in there had been a steady drop of water "which turned progressively into a stream" - although it was not raining at the time - and said there was some panic when the ceiling fell in.
He said that outside the theatre there was scaffolding and building work going on.
Allow Twitter content?
In December 2013, 76 people were injured, seven seriously, when part of a ceiling at London's Apollo Theatre collapsed during a show, while 1,200 people had to leave the Queen's Theatre in Shaftesbury Avenue, following a small fire during a matinee performance of Les Miserables.