The storm rolled in with little warning Saturday, toppling a concert stage at the Big Valley Jamboree in Camrose, Alta. (Submitted by Ken Meintzer)A severe windstorm that toppled a concert stage in Camrose, Alta., killing one person and injuring as many as 75, happened so fast that details of what happened are a blur, the event producer said Sunday.

Larry Werner, of Panhandle Productions Ltd., said there was a "hub of activity" with nearly 100 people on the stage or nearby for the annual Big Valley Jamboree shortly before Saturday's chaos.

He said a set change was in the works when the storm struck around 6 p.m. local time. Nashville-based country singer Billy Currington had just wrapped up, while actor and singer Kevin Costner was getting ready to perform with his band, Modern West.

'All of a sudden, there was sand everywhere, a sandstorm … and you couldn't see anything'— Brenda Casper

Witnesses said Currington and a band member were bloodied but not seriously hurt. Debris fell around Costner and his manager, Nick Meinama, but both escaped injury.

CFCW radio personality Danny Hooper was on the stage preparing to introduce the next act when high winds suddenly started to blow. He was advised to warn the crowd of an approaching storm, but only managed to say a few words before the stage was hit.

Werner was also on stage and said he and others worked furiously to get everybody off the stage.

"We were trying to get everybody down the stairs. It happened so fast you truly can't honestly remember half of it," Werner said.

Winds exceeded 100 km/h

Officials at Sunday's news conference stressed that the storm struck with very little notice, blasting winds that Environment Canada officials estimated at over 100 kilometres per hour.

"RCMP informed us at 5:55 p.m. about unconfirmed reports that a possible tornado had touched down in the Nisku area [just south of Edmonton], said Camrose police Chief Darrell Kambeitz. "We had people on the stage at 5:57 p.m., and the storm struck between 5:57 p.m. and 6 p.m."

Thousands of fans screamed and sought cover; some ran to nearby tents and trailers. A 20-year-old man was in a porta-potty when it was knocked over. He had to get 20 stitches across his head.

"All of a sudden, there was sand everywhere, a sandstorm … and you couldn't see anything," said concertgoer Brenda Casper. When she was able to raise her head "the stage was gone," she said.

Kambeitz said 21 people were taken to hospitals and two remained in critical condition. More than 50 others were treated for less serious injuries at the scene.

Heavy rain deluged the area for about an hour as emergency crews treated the injured and combed through the wreckage for more victims. Initial estimates put the number of people injured at 15.

Police have not disclosed the identity of the dead person, but friends told local media that it was Donna Moore of Lloydminster, and that she was killed when an enormous speaker fell on her.

Organizers criticized

Debbie South, a nurse at Edmonton's Royal Alexandra Hospital who attended the event, said organizers should have halted the concert a lot sooner, instead of just giving fans minutes to react to the severe weather.

"We think they should have gotten [people] out of there earlier. The storm was coming, everybody knew," she said.

The severe windstorm left the Big Valley Jamboree in chaos. (Sumbitted by Brad Saville)Nursing student Jessica Lubemsky leaped into action when the storm hit.

"It was utter shock. I went running over as fast as I could just because I knew first aid and I knew so many people were on that stage," she said.

"I had to do some splints for people with broken arms. There were a bunch of people with a bunch of bruises, broken bones."

On Sunday, construction cranes could be seen as workers continued to clear debris from the caved-in concert bowl.

"Members of the Edmonton fire and Camrose fire units worked relentlessly through the night to ensure the area was safe and clear," said Deputy Chief Don Rosland of the Camrose Fire Department.

Concert organizers announced Sunday morning the party was officially over and cancelled acts such as headliner Tim McGraw. Area highways clogged with motorhomes and RVs as an estimated 15,000 fans made their way home.

With files from The Canadian Press