The Whistler Blackcomb ski resort reopened Wednesday morning, with officials saying they've determined that ice caused a gondola tower to collapse the day before.

Doug Forseth, the senior vice-president of operations at Whistler Blackcomb, said experts inspected the damaged tower overnight and determined the damage was likely caused by what he called "ice jacking."

The damaged tower was constructed from two large pieces of metal tubing that were welded and bolted together, but somehow water managed to get inside the joint, Forseth said.

When the water froze, it expanded and caused the tower splice to rupture, a situation referred to as ice jacking, he said.

"This is very unusual. I can think of only one other case in North America where this has happened," he said.

Lift passed safety inspection

The problem was not spotted when the tower passed a safety inspection by the B.C. Safety Authority in October, Forseth said at a news conference in Whistler on Wednesday morning.

Crews work at the scene where a gondola tower partially collapsed. Darryl Dyck/Canadian Press

"I don't think that we were negligent or that people were missing anything. It's just that it was very difficult to understand. We don't know why there was water in the tower," he said.

The support towers on similar Doppelmayr-brand lifts at the resort, including the Wizard and Solar chairlifts on Blackcomb Mountain, were also checked overnight by resort staff and again on Wednesday morning by the B.C. Safety Authority.

"Preliminary inspection by B.C. safety officers has determined that this was an isolated incident of water contamination in a tower tube, which caused a tower joint flange to fail due to ice jacking," said Greg Paddon, safety manager with the safety authority.

Ski lifts on the Whistler Mountain side of the resort reopened Wednesday morning, and the remaining lifts on Blackcomb Mountain reopened before noon, minus the Excalibur Gondola, according to the resort's website.

"There is no justification at this time that other installations operating at Whistler Blackcomb have been affected by a similar failure. The B.C. Safety Authority does not anticipate rescinding operating permits on any lifts currently operating at Whistler Blackcomb other than the upper and lower Excalibur Gondola," Paddon said.

Passengers trapped for hours

Thirteen people suffered minor injuries on Tuesday when a tower that supports the cables on the Excalibur Gondola partially collapsed, leaving 30 gondola cabins dangling from a thick metal cable.

Whistler firefighters help rescue people stranded in gondola cabins on Tuesday afternoon. CBC

Several gondola cabins were damaged when they fell up to 10 metres to the ground, and one hit the roof of a bus shelter, while others remained suspended in the air. Remarkably, the most serious injury was a cracked vertebra.

The damaged tower was eventually secured with a construction crane, and the gondola's cable was also secured to prevent the lift's cabins from springing up into the air.

Firefighters then used a ladder truck to remove most of the passengers from most of the cabins, while ski patrollers lowered the passengers in two cabins to the ground using harnesses and ropes. The entire evacuation took about 3½ hours.

The Excalibur Gondola, which runs from Whistler Village up Blackcomb Mountain, was built in 1994 by Austrian-based Doppelmayr and undergoes an extensive safety check every year by the B.C. Safety Authority.

The gondola has an upper and lower section. The upper section of the gondola, which is independent of the lower section, was unaffected by the incident but was cleared immediately of passengers.

The Whistler Blackcomb resort, which will host the alpine ski events for the 2010 Winter Olympic Games, has a total of 38 lifts capable of carrying more than 65,000 people per hour.