Video recorded by an MBTA passenger shows the end door of a Red Line car wide open while the train was in motion.
The MBTA said Thursday that the incident happened Wednesday while the train was traveling to the North Quincy stop.
"At North Quincy Station, an MBTA employee who was a passenger on the train attempted unsuccessfully to close the end door," the MBTA said in a statement. "While the train was still berthed at North Quincy, the operator of the train then entered the car and closed and secured the end door."
The train continued southbound without any further issues, the MBTA said. The car is out of service as maintenance workers look into why the door was open.
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