A concert billed as one that would "rattle the foundations of the historic St James Complex in Auckland" did just that when chunks of plaster fell on to the heads of two concert-goers.

The pair were taken to hospital where one, a 17-year-old youth, required stitches and the other, a female, was checked for concussion.

They were struck by plaster that fell from a decorative portal during the Mint Chicks concert at the St James Theatre in Queen St last Wednesday night.

The Mint Chicks were playing as a support act for the Yeah Yeah Yeahs.

St James manager John Griffiths said the vibrations and sound waves from the music had dislodged the plaster in the theatre, which is a category-one building on the Historic Places Trust register.

"It's an old, old theatre, built in 1936, and there is a lot of ornate plasterwork," Mr Griffiths said.

"It was an exceptionally loud concert, the loudest there has been at St James for a long time."

He said the plaster chunks fell from one of the decorative portals in the building and ricocheted off another fixture on to the concert-goers.

Mr Griffiths said the pair were taken to hospital as a precautionary measure. He understood the youth required five stitches and the woman was checked for concussion and given a tetanus injection.

Other planned events had continued at the theatre, and yesterday engineers were checking the plasterwork to ensure it was stable.

The theatre's management was discussing possible compensation with the two injured people.

"My directors are very concerned about those eventualities," Mr Griffiths said. "We are very concerned when there is an injury, of course."

The pair's ticket prices had been refunded, and the theatre had offered to cover the costs of any direct damage, such as damaged clothing. The St James had also offered free tickets to other events at the theatre.

Mr Griffiths said the concert continued after the incident, but workers checked the ceiling for safety. Events at the theatre had continued as normal since then.

Neither of the injured people would comment to the Herald.

Jim Bell, Penrose team leader for the Department of Labour's workplace health and safety service, said businesses were obliged to notify the department only in cases of serious injury.

"However, the department will be making some preliminary inquiries with the theatre management to establish what happened, the extent of the injuries to audience members, and what the theatre is doing to ensure it doesn't happen again."

* In August 2001, about 10 people fell about half a metre through the dance floor at the St James after it partially collapsed during an Incubus concert. Nobody was hurt.