Cisco Ottawa Bluesfest executive director Mark Monahann said organizers had been monitoring the weather moments before a violent summer gale toppled the main stage at the festival Sunday night.
"Honestly, what we've been told, it was a very unusual situation. The fact that (the storm) brought that stage down and nothing else came down in the park is just a freak situation," Monahann said.
Witnesses say Cheap Trick band members were thrown off their feet but got off the stage safely. Five people were hospitalized for their injuries but later released, Monahan said.
"Everyone is shaken up but band and crew are all fine...Everyone is okay and we are so lucky to be alive and hope that all the fans are okay too," the band, best known for hits including "Surrender", "I Want You to Want Me" and "The Flame", said in a message posted on Facebook.
Video posted on YouTube within minutes of the storm's passing showed a collpased stage that had been propelled backward before crumpling and damaging a tractor-trailer truck parked behind it. Twisted shards of metal jutted out from the stage, which stood several stories tall before it was destroyed.
Concert-goer Leanne Wilson said the stage slowly heaved backwards and caved in.
"In less than 10 seconds it was gone," she said. "(Cheap Trick) were playing right until it fell. And then instantly everybody was just running and screaming."
Monahan said the stage was rented from a Montreal firm and was inspected regularly during the festival. The Ministry of Labour is surveying the site and will produce a report on the accident.
Bluesfest is one of North America's main musical events. The festival first took place in 1994 and has since grown from a one-stage, three-day event to a multi-staged, 12-day music showcase featuring some of the best international talent.