Members of the British rock band Radiohead said they are "shattered" by the death of their drum technician, who was killed after a stage collapsed at Toronto's Downsview Park hours before the band was scheduled to perform Saturday night.

Scott Johnson, 33, was pronounced dead at the scene after the massive stage collapsed.

"We have all been shattered by the loss of Scott Johnson, our friend and colleague," Radiohead drummer Phil Selway wrote on behalf of the band on Sunday.

"He was a lovely man, always positive, supportive and funny; a highly skilled and valued member of our great road crew. We will miss him very much. Our thoughts and love are with Scott's family and all those close to him."

Johnson had also worked as a drum tech -- the person responsible for setting up and tuning the band's drums -- for the British band Keane.

A large swath of Toronto's Downsview Park was cordoned off as investigators tried to pinpoint the cause of the fatal stage collapse at the multi-purpose venue.

Investigators with Toronto Police Services and the Ministry of Labour were on scene Sunday morning to assess the wreck of twisted metal.

Ministry spokesperson Matt Blajer said the massive structure is "still fairly unstable" and work is underway to ensure its safety. He said investigators are looking at whether safety regulations and standards were followed and staff were properly trained.

Efforts to review the scene the day before were hampered when darkness fell and authorities were forced to delay the investigation until first light Sunday.

The incident, which left metal pipes lying in a heap on the stage, didn't occur when fans were inside the concert venue. But, police said "a number of people" were on the stage at the time of the collapse, trying to prepare the area for the concert.

A 45-year-old man was transported to Sunnybrook hospital with a non-life-threatening head injury after the incident, which happened around 4 p.m. ET Saturday.

Toronto police Const. Tony Vella said Sunday the man was doing "much better" in hospital.

Two other males were injured, but were treated at the scene by paramedics.

An audience of about 40,000 people was expected to attend the sold-out concert, which officials cancelled shortly after the incident.

Ticketmaster posted a message to its website saying that all tickets will be refunded at point of purchase. Concertgoers who bought their tickets online or by phone will receive an automatic refund. Those who bought their tickets at a retail location can return them to the same location.

The stage for Radiohead was set up in the north-west corner of the large park, which is located in the north end of the city. The popular urban park hosts a number of large concerts and performances every year.

With files from The Canadian Press