(CNN) -- Canadian ski resort gondola cars that were left dangling and swaying with terrified skiers inside failed because ice buildup snapped a supporting tower, the resort said Thursday.
One gondola car is suspended above an icy creek at a ski resort near Whistler, British Columbia.
In a rare occurrence called ice-jacking, water seeped into the lower section of the lift tower and turned to ice Tuesday at Whistler Blackcomb resort, 177 kilometers (110 miles) north of Vancouver, a resort official said in a press release Thursday.
The lift hangs from a tower that is spliced into two parts.
Extremely cold temperatures caused the ice buildup that exerted 800 tons of pressure between the two parts that hold the tower together, causing them to rupture, according to Whistler Blackcomb.
The section of the lift affected by the accident had 15 cars going up the mountain and 15 coming down at the time, but they weren't carrying a lot of passengers, according to Doug Forseth, senior vice president of the resort.
He said 53 passengers had been rescued from the stranded cars.
No skiers at the Whistler, British Columbia, resort were seriously injured.
"The towers are not normally designed to allow for any water penetration and so this failure is a very unusual situation," said Warren Sparks, senior vice president of Doppelmayr Canada, the engineering firm that investigated the accident.
They are trying to figure out what caused the water to pool. He said independent structural engineers are examining the tower from Vancouver-based CVMM Consulting Engineers.
"The evidence so far indicates a sudden rupture rather than a fatigue failure over an extended period," Sparks said.
At least two gondola cars broke away and hit the ground, both from relatively low heights near the tower that split, and caused the system's heavy cable line to slacken, according to Tyler Noble, a reporter for CNNRadio affiliate CKNW in Vancouver.
"One hit a bus stop and the other hit a house," Noble said Wednesday. "Another one was suspended over a creek, but everyone is out of that car."
The broken Excaliber Gondola was not operating Thursday.
Whistler engineers checked eight similar towers across the two mountains of the resort. All passed those inspections, and are open Thursday, the release said.
The British Columbia Authority says it does not expect to rescind operating permits on any lifts at the resort, other than the Excaliber Gondola.
Jeff Colburn, general manager of Silver Mountain Resort in Kellogg, Idaho, said a lift tower at his resort was similarly damaged by ice in December 2006.
The damage was discovered in the morning before the slopes opened, so no one was endangered, he said.
The damaged tower was replaced in about three weeks, Colburn said, and the resort's business was not significantly disrupted.
"We check our towers in the summer now, and we also check before we open up for ski season as well just to make sure they don't have any water in them, and we've worked with the manufacturers," he said.
Holes have been drilled in the bases of towers so that water can drain out, Colburn said.
CNN's Ashley Fantz and Jim Kavanagh contributed to this report.
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