Investigators are trying to figure out why a MBTA commuter rail train made contact with the rear of an Amtrak train Wednesday afternoon near Boston's South Station.
The Amtrak train was leaving a nearby maintenance facility and was being followed by a commuter rail train, operated by Keolis.
The Amtrak train was stopped at a signal when the commuter train hit the back of the Amtrak locomotive at a slow speed.
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No one was hurt, and no passengers were on board either train at the time.