BOSTON (WHDH) - Buses temporarily replaced subway service on a stretch of the Red Line for part of the Thursday morning commute after firefighters responded to a disabled train at the Charles/MGH MBTA station.

T officials said the operator of the train had noticed smoke and a possible fire under his train as it crossed the Longfellow Bridge into Boston. Fire crews responding to a reported fire underneath a train around 5:45 a.m. found that all passengers had already self-evacuated and there were no injuries.

Power was turned off to the third rail so that firefighters could investigate what was causing the fire, the MBTA said in a statement.

Deputy Fire Chief James Greene said a broken water pipe in the station initially hindered crews ability to fight the fire but it was quickly extinguished.

In an update, officials said the smoke under the train had come from an air compressor control box.

Responding to the scene, MBTA General Manager Phillip Eng told reporters the incident was a problem linked to the aging infrastructure he is trying to restore, along with trying to restore rider confidence.

“We have work to do, obviously and I want folks to know that we are going to be persistent and determined, and they will see a system that they can be proud of,” Eng said.

The MBTA said Red Line service was fully-restored around 8:40 a.m.

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