A performance of Titanic the Musical was abandoned after debris fell on to the stage during its opening night in Southampton.
Audience members at the Mayflower Theatre said items began falling shortly after the scene in which the ship hits the iceberg.
An announcer said the show was being halted for “health and safety reasons”.
The Southampton run coincides with the 106th anniversary of Titanic’s maiden voyage from the city in April 1912.
Associate producer Michael Ockwell said: “You couldn’t make it up… the irony isn’t lost on us.”
A theatre spokesman said plaster from a backstage wall had fallen on to the stage but it was “not a major structural issue”.
“With the safety of the cast in mind, we made the sensible decision to cancel the second act of the show,” he added.
Claire Cleaver, who was attending Thursday’s show with her niece, said she initially thought it was an on-stage effect.
“It was quite frightening at first as we didn’t know what was going on but the Mayflower handled it very well and there was no panic,” she added.
“It’s very ironic being the first showing of the Titanic musical and then the show itself sinking. It was a fantastic show, it was so disappointing.”
Others posted their reaction on social media.
The theatre said no-one was injured and Friday evening’s performance was expected to go ahead as planned following repair work.
Audience members have been told their tickets can be refunded or exchanged.
During the ten-day run – its first in Southampton – a special midnight performance coinciding with the time the ship sank in April 1912 is due to take place on Saturday.
Titanic the Musical opened on Broadway in 1997 and has won Tony Awards including best musical and best score.