CARRABASSETT VALLEY — A Maine ski resort that’s responsible for two of three chairlift mechanical failures that led to injuries in the past five years is working to make sure it doesn’t happen again.

Sugarloaf is spending $1.5 million to make improvements after a chairlift malfunction allowed it to move in reverse last March, injuring seven skiers.

Workers are replacing the drivetrain on the King Pine chairlift that malfunctioned and have replaced the gearbox on a sister lift of a similar design, Timberline. They’ve also upgraded the brakes on seven other lifts to ensure no rollbacks. Another aging lift was removed altogether.

“We’re making these lifts as safe as possible with the most modern standards and components,” said Rich “Crusher” Wilkinson, vice president of mountain operations. “We don’t want to have any more lift incidents here.”

Nationwide, such incidents are rare. Skiers are far more likely to be hurt driving to the resort or skiing down the slopes than riding on lifts, according to the National Ski Areas Association.

There have been only six mechanical failures resulting in injuries in the past 15 years in the U.S., and the last fatality linked to a mechanical problem was in 1993 in California, officials say.

At Sugarloaf, investigators determined the mechanical failure on the 27-year-old King Pine quad was caused by a broken drive shaft in a gearbox that allowed the lift to begin moving backward. A faulty switch prevented an anti-rollback system from locking the lift in place, and then the emergency braking system failed to automatically activate.

The Borvig-manufactured lift traveled about 400 feet in reverse, prompting some skiers to bail out, before it stopped three to five seconds later. Three of the seven injured skiers were taken to a hospital.

Five years earlier, high wind contributed to another lift accident in which some chairs on Sugarloaf’s Spillway East plummeted 25 to 30 feet onto the snowy surface below, injuring eight skiers and trapping others in the air for more than an hour. That 35-year-old lift was replaced entirely with a new model.

All claims from the 2010 accident have been settled, and there have been no new claims from the March incident, said Noelle Tuttle, a Sugarloaf spokeswoman.

Both of Sugarloaf’s accidents involved older lifts that are part of an aging infrastructure at many resorts. Nationwide, most lifts were installed during the 1970s, ’80s and ’90s, and hundreds of old lifts remain in service, industry officials say.

Skier Ron Jacques said he has confidence in Sugarloaf to make needed repairs, but he acknowledged the resort’s track record hasn’t been good in recent years.

“Their number has come up too often in the past few years,” said Jacques, owner of the Ski Depot store in Jay. But, he added, no machinery is 100 percent foolproof.

After the March accident, Partek Ski Lifts, which provides technical support for Borvig lifts like the one that failed, warned operators of about 170 similar Borvig and Partek lifts to replace switches. Sugarloaf also shut down a similar lift, Timberline, which served the mountain’s summit.

Over the summer, in addition to regular maintenance, workers drained the oil from the gearboxes on all of the lifts and used a scope to examine components for excessive wear. That led to the overhaul of the gearbox on one lift, Wilkinson said.

The Maine Board of Elevator and Tramway Safety has not released its final report on its investigation, but it issued recommendations over the summer to ski resorts with similar lifts, said spokesman Doug Dunbar.

Maine ski resorts have a good track record, and there’s never been a chairlift fatality caused by a mechanical problem in Maine. “While any accident is too many, chairlift travel remains very safe in Maine and throughout the U.S.,” he said.