Police responded to the Piccadilly Theater in the city's West End area around 8 p.m. after part of the ceiling crashed down. More than 1,000 people evacuated the venue, the BBC reported.
BBC journalist Iain Haddow was at the play and said the collapse happened 20 minutes into the show. He said water had been dripping, "which turned progressively into a stream."
Actor Wendell Pierce -- known for his work in HBO's "The Wire," the 2014 film "Selma" and numerous other TV roles -- plays the main character of Willy Loman. He apologized to theatergoers outside.
“I did not mean for it to go like this,” he said in a video posted to Twitter. "I would like to thank you all, for one, safely evacuating. We apologize and we're glad that no one's hurt."