A southbound Downeaster train was disabled after a low-speed derailment in South Portland on Tuesday afternoon.

None of the 36 passengers on board were injured.

The train had left Portland at about 2:25 p.m. and derailed shortly after crossing the Fore River in South Portland near the Sprague Energy tank farm. At about 4:45 p.m., an out-of-service Amtrak engine that was in the area pushed the train back to the Portland Transportation Center.

The passengers were taken to Boston on a bus, said Amtrak spokesperson Christina Leeds.

As a result of the derailment, train 686, which is disabled, and train 687, which was due to leave Boston at 6:05 p.m., were canceled.

Train 685, which was scheduled to leave Boston at 5 p.m., will hold and leave Boston at 6:05 p.m.

Leeds said the cause of the accident is under investigation.

“It’s something we are looking into,” she said. “We don’t have a cause at this point in time.”

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