Keolis: Wheel separation caused Commuter Rail derailment

Why did wheel fall off Commuter Rail car? Keolis investigating train derailment

WALTHAM, Mass. — A derailed commuter rail train stranded Fitchburg line passengers near Waverly Station early Tuesday morning.

The inbound train was stopped near Waverly Station on Trapelo Road in Waltham.

MBTA officials said 800 passengers aboard the train were transferred to another train.

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A Keolis spokesperson said the train was involved in an "upright derailment" near Waltham that may have been caused by a mechanical issue.

According to Keolis, the initial investigation indicated a single-level car had a wheel separation between Waltham and Waverley Stations -- though it's unclear at this point why.

The separation prompted the derailment, Keolis said.

A crane was brought in to 're-rail' the train and remove the equipment from the tracks.

"The vehicle in question and all associated components will be quarantined in order to conduct a detailed engineering analysis," Keolis said in a statement. "As a result of this incident and as a precautionary measure, an inspection of all coaches with the same equipment is now underway and is expected to be complete before the start of the evening commute."