A traction motor underneath the middle car of a five-car New Canaan train grounded out during the Monday morning commute, causing a serious smoke condition on board according to Metro-North officials.

Passengers on the 7:33 a.m. out of New Canaan opened the four emergency windows, which helped clear out the smoke, and then moved to adjacent cars. No injuries were reported.

Metro-North officials said fire department assistance wasn't needed.

According a statement released by Metro-North, a traction motor transforms electricity into movement. When it grounds out -- essentially blows a fuse -- it turns itself off. Once the power is off, it does not continue. The cause is under investigation; however, officials said the usual culprit is water intrusion in the motor.

The M-6 car was built in 1995.

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Initially, a customer hit a buzzer on the ceiling of the car to notify the crew that something was awry," officials said. "The engineer brought the train to a halt near Woodlawn and the conductor went toward the troubled car."

After the car was emptied, the engineer requested permission to move the train off the mainline into a nearby siding to minimize impacts to other rush hour service.

The train was delayed while the crew awaited mechanical and transportation supervisors who inspected the train and determined that it was OK to continue its trip to Grand Central.

The train, scheduled to arrive at Grand Central at 8:39 a.m., arrived 39 minutes late.