Collapsed Concert Stage at Downsview Park in Toronto

An aerial view shows the collapsed concert stage at Downsview Park in Toronto, where Radiohead were due to perform. Tara Walton/AP Photo.

Tara Walton

TORONTO (AP) — Investigators combed through the wreckage of a Toronto stage collapse Sunday, trying to determine what caused the structure to come crashing down hours ahead of a Radiohead concert, killing the band's drum technician and injuring three other people.

Radiohead representative Laura Eldeiry confirmed the man killed was Scott Johnson, the drum technician for the British band. Toronto Police spokesman Tony Vella said the British man was in his mid-30s. He was trapped under the rubble and pronounced dead at the scene.

Officials from the Ontario Ministry of Labor searched through the wreckage for clues to the cause of the collapse Saturday in Downsview Park. They were also investigating whether safety regulations and standards were followed and if staff were properly trained.

Ministry spokesman Matt Blajer said the massive structure is "still fairly unstable" and work is under way to make it safe.

He said the investigation is "fairly complex" and it could take some time to figure out exactly what happened.

Three others were injured when the top portion of the stage collapsed as the crew was setting up. Vella said a 45-year-old man hospitalized with a head injury was improving and his life was not in danger. The other two were treated at the scene.

The sold-out concert was cancelled. Radiohead said on its website that fans will get refunds.