Less than five years ago, Rick Tonge was riding a chairlift at Sugarloaf ski resort in Maine when five chairs -- including his -- plummeted 30 feet to the snowy ground below, injuring him and his son.

Then over the weekend, another chairlift at Sugarloaf malfunctioned by going backward, prompting some frightened skiers to bail out and raising questions about the safety of aging infrastructure at New England's ski resorts.

"It's got to bring it to people's attention that something's got to be done," Tonge said Sunday from his home in Belgrade. "This is an old mountain. It's been around a long time."

The resort said Sunday a preliminary investigation found that a gearbox on the lift malfunctioned and effectively disabled two brake systems. A third backup brake also didn't deploy properly and a lift attendant pulled an emergency brake to bring it to a halt after chairs slid about 450 feet, Sugarloaf spokesman Ethan Austin said in an emailed statement.

Seven skiers were hurt at the resort, which is hosting the U.S. national ski championships starting this week with top skiers like Lindsey Vonn and Mikaela Shiffrin.

Two of the three injured skiers transported to a hospital 40 miles away were treated and released; the third was transported to another hospital, a hospital spokeswoman said Sunday. The condition of the third skier was not known, but the resort said the injuries were not believed to be life threatening.

The ski industry points out that riding a chairlift is safer than riding an elevator, and there has not been a death due to mechanical malfunction since 1993.

But there have been at least four other malfunctions causing injury since 2000 nationwide, according to the National Ski Areas Association, but the ages of those lifts were unknown.

At Sugarloaf, the December 2010 incident involved a 35-year-old double chairlift -- since replaced -- that was being worked on while skiers were on board. Saturday's incident involved a 27-year-old quad chairlift.

The King Pine lift that malfunctioned over the weekend had passed its annual state inspection and a dynamic load test that's required every seven years last fall, Austin said.

The gearbox that failed, effectively blocking two of the three brake systems from deploying, had just received preventative maintenance the day before, he said, adding that it's too early to know if procedures will be changed.

Tonge, whose back was hurt in 2010, worries that the resort has been slow to upgrade aging equipment. "They have plans in the works to replace lifts. There have been plans right along. But they're late," he said.

Older lifts aren't necessarily unsafe if they're properly maintained, but they become functionally obsolete because skiers reject them as too slow and as they become too expensive to maintain.

"Lifts aren't designed to last forever," said Mark Di Nola, a ski safety consultant in New Hampshire who serves as an expert witness in ski-related lawsuits.

Steve Kircher, president of eastern operations for Boyne Resorts, which operates Sugarloaf, took exception to the notion that aging chairlifts lifts 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. 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," he said.

The incident has not shaken the confidence of the U.S. Ski and Snowboarding Association as Sugarloaf prepares to host the national championships.

"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," spokesman Tom Kelly said.

At least one skier who was on the King Pine lift when it went backward was skiing again on Sunday.

Greg Hoffmeister of Needham, Massachusetts, said he and his daughter jumped out from about 10 feet up, while his wife and two other daughters in another chair were rescued by the ski patrol.

"It was scary for sure," he said.