The lift, carrying more than 200 skiers, was stopped by an emergency brake that engaged automatically, contrary to early reports that a worker manually activated it.
A team of engineers completed their preliminary review and investigation at the ski resort in Carrabassett Valley, a small town that's also home to a skiing and snowboarding academy. They said they were correcting the design flaw that was identified.
Sugarloaf's general manager said he was grateful to have "a clearer understanding of what occurred" in the Saturday accident.
"Our first thoughts remain with those injured, and our sincere hope for their speedy recovery," general manager John Diller said in a statement.
The chairlift mishap, the second in five years to cause injuries at Sugarloaf, came just days before top skiers began arriving for the national alpine championships, which started Wednesday.
The day before the mechanical failure, workers had run tests on all of the chairlifts at the resort for excessive vibration and found nothing pointing to any imminent problem with the King Pine lift, the resort said.
The fractured drive shaft in the secondary gearbox caused it to separate from the main gearbox, knocking the primary brakes out of commission and necessitating the emergency brake to stop the lift, the resort said.
Another brake system, called a drop dog, akin to putting a stick in the spokes of a spinning bicycle wheel, failed to activate because of an electrical switch that was the wrong type for the application, officials said.
"The investigation indicates that, had an appropriate switch been included in the system, the drop dog would have deployed and the rollback would have stopped immediately," Sugarloaf said in a statement.
Sugarloaf and another ski resort, Sunday River, located in Newry, were replacing the switches on all similar chairlifts. Sugarloaf and Petoskey, Michigan-based Boyne Resorts, the operator of Sugarloaf and Sunday River, have been in touch with the chairlift's parts manufacturer to share the findings, which could affect more lifts across the country, officials said.
Three of the seven injured skiers were transported to a hospital on Saturday. Two of them were treated and released; the condition of the third was unknown.
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 chairlift malfunctions causing injury since 2000 nationwide, the National Ski Areas Association said.