The derailment of a Metro-North train as it slowly maneuvered in a New Canaan yard last week was caused by a faulty switch, a preliminary investigation concluded.

Metro-North spokesman Aaron Donovan said Wednesday a 1/8-inch gap in a switch that allows trains to change tracks caused the derailment. The switch has since been repaired, he said.

“The preliminary finding is that this appears to have been a low-speed wheel climb derailment,” Donovan said.

“This type of derailment occurs when a wheel of a train that is moving slowly experiences a force in a horizontal direction that exceeds the vertical force created by the weight of the train, and friction between the wheel and the rail causes the wheel’s flange to climb upward in the inner-side of the rail,” he said in a statement.

“In this case, some additional horizontal force was caused by a 1/8-inch gap at a switch,” Donovan said. “Repairs have been made to the switch involved.”

The train derailed on April 14 as it was slowly moving in the New Canaan station’s yard. The mishap caused delays of up to 60 minutes for commuters because the disabled train blocked other rail traffic.

No passengers were on board and no crew members were hurt, Metro-North officials said.

Judd Everhart, a spokesman for the state Department of Transportation, said the agency is satisfied with Metro-North’s inspection and maintenance programs.

“Metro-North is responsible for the day-to-day inspection and maintenance of the New Haven Line, its three branches and all equipment, and the DOT is very satisfied with their work in that regard,” Everhart said.

“This event falls into the category of the relatively minor and rare, and we are confident that it has been properly addressed,” Everhart said.

Jim Cameron, founder of the Commuter Action Group, said the derailment was minor.

“This was a very minor derailment at slow speed,” Cameron said. “I'm confident (federal regulators) will have Metro-North inspect all similar switches.”

State Sen. Toni Boucher, R-Wilton, a ranking member on the General Assembly’s Transportation Committee, said she’s thankful the train was moving slowly and not carrying passengers.

“I think we have to leave it in their hands,” Boucher said. “The public should be made aware, and we have to trust they will improve their processes.”

Boucher said a recent change in Metro-North’s leadership has made her more confident of the railroad’s focus on safety, inspections and maintenance.

Metro-North has a recent history of serious accidents, including the May 2013 derailment in Bridgeport that injured more than 70 passengers. The cause of the accident was determined to be a section of broken track.

In December 2013, a Metro-North train derailed in the Bronx after the engineer fell asleep, killing four people and injuring 63.