Two boys were taken to hospital after receiving neck wounds during an opening night performance of Sweeney Todd at a school in Auckland, New Zealand.
The musical features a barber who murders his customers by slitting their throats and selling their remains to a pie shop.
One of the boys, both aged 16, was more seriously hurt but Auckland Hospital said both were in a stable condition.
Saint Kentigern College said it was “distressed” over what happened.
“Plays and performances are a big part of all school life” the private school said in a statement, saying the incident was being thoroughly investigated.
“We are also very focused on helping other cast and crew members, along with the wider school community and have offered all students counselling.”
It has postponed Thursday’s performance of the play.
It added that the boys were expected to be discharged from hospital on Thursday
Police are also investigating the incident, which happened on the opening night on Wednesday, but said they were treating it as an accident.
“It’s not a criminal inquiry. In this instance the play is not the reality,” said the police spokesman, according to local media.
New Zealand’s health and safety authorities are also reported to be investigating the incident.
It is not yet clear how the teenagers came to suffer the cuts. New Zealand media said there was speculation they had been hurt by a cut-throat razor prop or by a trap-door chute used to exit the stage.