CAMROSE, Alta. - Construction cranes replaced country music fans Sunday at Alberta's Big Valley Jamboree as workers cleaned up after a devastating storm that smashed into the main concert stage, killing one person and injuring as many as 75 others.

The concert bowl caved in after wild winds hit the popular annual festival in Camrose, about 100 kilometres southeast of Edmonton, around suppertime on Saturday.

Festival organizer Panhandle Productions Ltd., said two people remained in hospital in critical condition.

Officials said about 21 of the dozens of people who were injured had to be taken to medical facilities for treatment. They offered no details about the one death, although Camrose police Chief Darrell Kambeitz said it was "as a result of debris coming down from the stage."

At a news conference on the site Sunday, officials made it clear that the storm struck with very little notice.

"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 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."

Producer Larry Werner said his office also got a call saying a severe windstorm was heading directly for the venue.

"At that time I ran for the stage from our production office. (Nashville musician) Billy Currington was in the process of wrapping up his set and we immediately let him know he had to get off the stage so we could announce to the crowd that we had to clear the concert bowl."

Werner paused Sunday when reporters asked him what he would say to people who thought there should have been more notice.

"What do you say?" he asked. "We worked with what we had to work with. I wish nobody was hurt. I wish it never happened. It did, and now we have to deal with it."

Werner said producers have had to shut down the concert three times in the last 17 years. "The procedures followed for those weather fronts were the same as the procedures followed (Saturday)."

Neither Werner nor Kambeitz could say immediately why the structure failed, or how long it would take to get answers. Provincial officials are helping with the investigation.

Aaron Vandermeulen, 16, of Regina stood staring as the giant construction cranes carefully tried to pry apart twisted piles of collapsed metal stage supports.

The teen, who was helping to string cable for video cameras on stage when the high winds struck, absently touched a large scrape across his nose as he recalled the terrifying experience.

"One of the guys working in the sound booth came in and said, 'You'd better get out of here.' I kind of looked to the side and I see this huge wall of brown dirt kind of flying towards us all," Vandermeulen said.

He dropped the cable he was carrying and ran towards a large semi-trailer, hoping it would shelter him from the storm.

"As I was coming down the stairs, I looked back and saw everything falling. Two of the metal support poles fell down in front of me. The tarp falls down with it and knocks me."

He struggled up through the debris and dove behind the big rig.

It was then he realized that the stage had collapsed and people were trapped underneath the debris.

"We could hear people screaming and people trying to lift other people out (of the debris). It was a terrifying sight."

Debbie South, a nurse at Edmonton's Royal Alexandra Hospital who attended the event, said as soon as she heard of the disaster, she rushed from her camper towards a cacophony of police and ambulance sirens.

What she saw was a jumble of metal and a scene of chaos as emergency workers tried to figure out where to start to look for casualties in the driving rain.

"They were just trying to triage and get people organized," said South, still somewhat in shock at the disastrous turn the weekend had taken.

As South talked of her experiences Sunday, a group of people behind her picked through the flattened remains of a blue tent that had been blasted by winds that Environment Canada officials estimated at over 100 kilometres per hour.

Two friends, who had been on seats on stage with the performers, were buried under debris and had to shimmy through a narrow gap to get out from under it, said Michele Lamoureux.

"They're in shock right now. Everything of theirs was destroyed."

Parents were screaming for their children and the shocked couple helped pull people out of the wreckage.

"They were walking around like zombies after that. They couldn't pull it together," Lamoureux said.

South 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," said South.

But Lamoureux suggested that the high winds arrived suddenly and that there was little anyone could do.

"Everybody wants to blame someone. I don't know that we can do that," she said.

Dan Kulak, a severe weather meteorologist with Environment Canada, said a phenomenon known as plough winds, not a tornado, was responsible for the destruction.

He said the high winds can travel up to 20 kilometres in front of a storm, which is exactly the scenario that developed Saturday as a 200-kilometre long weather system moved west through Alberta.

Such winds are actually fairly common during summer weather in the province.

"They cause the majority of damage in Alberta," Kulak said.

Severe weather warnings had been issued for the area before the storm struck. But Kulak pointed out that it can be very difficult to predict the behaviour of such winds.

"It's essentially an act of God. Everybody did as much as they possibly could have done," Kulak said.

It was "freakish" that the winds tore down the event stage, but did little damage in the nearby community, Kulak added.

To give some perspective on how powerful the winds were, Kulak said a tornado that ripped through Edmonton 22 years ago, killing 26 people, was an F-4 wind event, which packs of winds of over 300 kilometres per hour.

The blast that ripped through the Camrose area was, at most, an F-1, which carries winds of about 100 kilometres per hour.

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