The Sugarloaf ski resort said Sunday that a “major mechanical failure” in a gearbox appears to have caused a braking malfunction and the resulting chairlift “rollback” accident that injured seven people at the Carrabassett Valley facility Saturday.

“Though it is ongoing, the investigation’s preliminary findings revealed that the trigger for the incident was a major mechanical failure in one of two gearboxes connecting the lift’s electric motor to its drive bullwheel,” Ethan Austin, a spokesman for Sugarloaf Mountain Resort, said in a news release. “A bullwheel is a large metal wheel around which the lift cable – which supports the chairs – is tensioned.”

At about 11:30 a.m. Saturday, a chairlift carrying more than 200 skiers slid backward for about 450 feet, prompting some skiers to jump off.

It took the Sugarloaf Ski Patrol and other rescuers nearly two hours to get stranded skiers off the chairlift.

Seven skiers were treated for an assortment of injuries, and three of them were transported to Franklin Memorial Hospital in Farmington, Austin said. Two were treated and released, and the third was transferred to Central Maine Medical Center in Lewiston, according to the Farmington hospital.

The skier taken to CMMC is not believed to have suffered a life-threatening injury, Austin said. He said he was unable to identify the skiers who were injured because of privacy laws.

Austin said Sunday that several of the injuries occurred when people were hit by chairlifts near the chairlift terminal. Others suffered injuries “consistent with what you would expect from a 10-foot fall” from a chairlift, he said.

In Sugarloaf’s statement Sunday, Austin said that “just one day before the incident, the gearbox passed a sophisticated routine preventive maintenance procedure intended to identify potential problems.”

He said “the gearbox failure effectively decoupled the bullwheel from the lift’s primary service brake, which is located on the drive shaft between the two gearboxes, and its anti-reverse brake, which is the first of three redundant backup mechanisms for preventing reverse travel.”

At that point, Austin said, “the emergency bullwheel brake, which uses calipers to apply braking pressure to the flange of the bullwheel itself, was applied by the lift attendant. This brake slowed the speed of the rollback and ultimately brought the lift to a stop. The application of the emergency brake by the lift attendant likely prevented a more extensive rollback.

“The cause of the gearbox failure and the failure of the drop dog to deploy as designed both remain under investigation,” Austin said. “It is likely that determining the root cause of these failures will require extensive analysis.”

For a second day Sunday, John Burpee, chief inspector for the state Board of Elevator and Tramway Safety, which regulates chairlifts, was at Sugarloaf to look into the accident. Burpee will return to the resort Tuesday, said Doug Dunbar, a spokesman for the agency.

Dunbar said the King Pine chairlift – the one that malfunctioned Saturday – passed its annual inspection in October. He said there have been no reports of problems, complaints or concerns since that inspection.

“Although problems with any mechanical system can happen, the safety track record of chairlifts in Maine is quite good,” Dunbar said Sunday in a written statement.

The incident took place just days before Sugarloaf hosts the U.S. national ski championships. The event will feature top skiers such as Lindsey Vonn and Mikaela Shiffrin, The Associated Press reported.

“We have been in touch with Sugarloaf. The lift in question has no impact on our event. We are confident in Sugarloaf’s ability to conduct our U.S. Championships,” Tom Kelly, spokesman for the U.S. Ski and Snowboarding Association, told the AP.

This was the second chairlift malfunction in five years at Sugarloaf. In 2010, eight skiers were injured when high winds caused a derailment and five chairs toppled 30 feet to the snowy ground.

Rick Tonge of Belgrade was one of the skiers injured five years ago, along with his son.

“It’s got to bring it to people’s attention that something’s got to be done,” Tonge told the AP on Sunday. “This is an old mountain. It has been around a long time.”

Greg Hoffmeister of Needham, Massachusetts, was riding the King Pine chairlift when it went backward Saturday. He didn’t let that deter him from returning to the slopes Sunday. He and his daughter had to jump about 10 feet to safety, and his wife and two other daughters in another chair had to be rescued.

“It was scary for sure,” Hoffmeister told the AP.

Meanwhile Sunday, others in the ski industry closely watched developments in Carrabassett Valley, and a ski safety consultant said a chairlift malfunction involving a rollback is unusual.

“I can’t tell you I have seen a lot of them,” said Mark Di Nola of RyeRisk Consulting in Manchester, New Hampshire.

Sugarloaf operates 15 chairlifts. The King Pine lift was installed in 1988 and was manufactured by Borvig Ski Lifts, which closed in 1993. There are only a handful of ski lift manufacturers.

The lift will remain out of commission indefinitely.

Austin said King Pine is inspected daily, biweekly and monthly by staff, and undergoes an annual review by the Board of Elevator and Tramway Safety. He said the state also requires every chairlift to undergo a full dynamic load test every seven years. The King Pine lift was put through that test in October.

“So it was thoroughly tested in the last several months,” Austin said.

The Sugarloaf Mountain Resort, which has 153 trails and glades, is owned by CNL Lifestyle Properties, a Florida real estate investment trust, and is operated by Boyne Resorts of Michigan. The first ski trail on Sugarloaf opened in 1953. Today it is the largest ski resort east of the Mississippi, in terms of acreage available for skiing.

Di Nola said it is unusual for a ski resort to experience two chairlift accidents.

Ski industry standards call for lift operators to be trained annually, he said, but there is no standard that addresses how often lifts should be replaced.

Di Nola said the owners of the 27-year-old King Pine lift at Sugarloaf have gotten a useful life out of it.

“I can say it is not modern, with new technology, but how long lifts are supposed to last, I can’t tell you,” he said.

He said there are other ski lifts of similar age at resorts across the country.

“Is that a cause for concern? It could be,” he said.

Steve Kircher, president of eastern operations for Boyne Resorts, took exception to the notion that aging chairlifts are problematic.

“Having literally grown up in the ski industry, I can tell you that age of equipment generally does not translate into higher risk,” Kircher told the AP. “There are lifts operating successfully all over the world that are considerably older than King Pine. I’ve also been around long enough to know that new lifts can have mechanical issues.”

Ski lift industry standards, which are voluntary, are set and overseen by the American National Standards Institute, a private group.

Saturday’s accident has been followed closely by other ski resort operators, both nationally and in Maine.

Sarah Devlin, spokesman for Sunday River resort in Newry, said a ski lift accident always brings the issue of safety to the forefront.

“Safety is something we do consistently on a daily basis,” she said.

Christopher Farmer, general manager of Saddleback Maine in Sandy River Plantation, said he had no comment other than to praise the handling of the accident by the Sugarloaf staff and ski patrol.

Whether the accident will have negative fallout for the state’s ski industry as it begins to wind down for the season is unclear.

Austin, the Sugarloaf spokesman, said it is understandable for skiers there to have safety concerns after Saturday’s events. He said the resort will work hard to retain their trust by investigating the accident thoroughly and reporting the results promptly.

“It is a matter of demonstrating our dedication to safety, and part of that is aggressively investigating what happened (Saturday), sharing it and moving on from there,” Austin said.

Injuries and deaths from ski lift malfunctions are rare, according to the industry.

The National Ski Areas Association, a trade group for ski resort operators, said that from 1973 to 2012 there were 13 deaths and 62 injuries from lift malfunctions and falls in the U.S.

But ski lifts do have problems regularly. On March 5, skiers in 20 cable cars were stranded for two hours in the Italian Dolomites when a tree fell on a cable and cut off power.

And in New Mexico, about 80 skiers were left dangling 25 feet above the ground Feb. 15 at the Pajarito Mountain ski resort when a ski lift became stuck. Some witnesses said it took about 90 minutes to be rescued.

Morning Sentinel Staff Writer Kaitlin Schroeder contributed to this report.