Three of the cars on the Adirondack Scenic Railroad's Polar Express went off the tracks Thursday night and crews are trying to find out why. Our Sarah Blazonis has details.

UTICA, N.Y. -- The Adirondack Scenic Railroad's Polar Express makes 33 journeys from Utica to the North Pole, also known as Holland Patent, every holiday season. Trip number 20 left Union Station Thursday night, but didn't go according to plan.

"Literally, we were a half mile from the station and my engineer reported a bit of a drag on the engine," said Al Heywood, an Adirondack Scenic Railroad volunteer who was the conductor on Thursday's train.

Three rear cars had left the tracks, but stayed upright. One railway volunteer sustained minor injuries, but the 370 passengers were unharmed.

Crews worked Friday to determine what caused the railroad's first accident in its 20 year history.

The rear locomotive had to make kind of an unusual journey down the tracks. Two cranes had to make sure it was properly positioned on the tracks before it could be moved so crews could get in to take a closer look at what could've caused the derailment.

The 12 miles of track traveled by the Polar Express are owned by Mohawk, Adirondack and Northern Railroad. Scenic Railroad officials say they're checked regularly by inspectors and a tool known as a geometry car.

"It is miraculous. It can sense if there's a hairline crack in a rail that you can't even see, if there's a loose bolt," said Heywood. "When it gets to the end of a trip, it prints out a little ticket that says, 'Here's all the things that need to be fixed.’"

Friday's Polar Express trains were canceled by the railroad so the Federal Railroad Administration could complete work at the scene.

The Adirondack Scenic Railroad says passengers on the derailed or canceled trains will be offered credit for a future trip. Saturday's Polar Express journeys were expected to run as scheduled.