A six-car Boston subway train with passengers traveled several stations without a driver before MBTA workers were able to stop it by shutting off the third rail. Investigators are looking into possible operator error as the cause for the 10 December incident, Massachusetts Transportation Secretary Stephanie Pollack said.

Pollack said that before the Red Line train left the Braintree station, the train's operator got off to perform a routine task when it began to roll forward. According to The Boston Globe, the train travelled non-stop through Quincy Adams, Quincy Center and Wollaston stations, before MBTA workers were able to stop it past North Quincy Station.

MBTA spokesman Joe Pesaturo said that no passengers were injured during the morning incident, but the 51-year-old operator suffered minor injuries after being brushed by the train. The operator, who has worked for the MBTA for over 28 years and whose name has not been released, was treated and later released, Pesaturo said.

"Something happened that should not have been able to happen, [and] we put our passengers in danger," Pollack said. The transportation secretary described the incident as unacceptable and promised to make improvements. The Globe reported that investigators will look into whether two sets of brakes were "properly deployed" when the operator got off the train.

Massachusetts Government Charlie Baker said the controls of the train "had been manipulated" and said he was confident it was an isolated incident. "The discussion that's going to take place on our end is negligence versus something else," Baker said. "It's pretty clear that the main control that drives the train was tampered with."

According to CBS News, passengers were confused when the incident began. Passengers reportedly knocked on the conductor booth after the lights went out but did not find the conductor. WBZ-TV spokes to passenger Fernanda Daly, who said that at first passengers believed there was a gunshot and that someone had gotten injured. Some passengers attempted to break windows and others tried to open the doors. "It was just kind of scary," she said.

State officials briefed on the investigation said that terrorism was not suspected. According to The Globe, the FBI had been in contact with Transit Police early on but was no longer involved in the case. Once the train was stopped, MBTA workers got on the train and took it to the JFK/UMass Station, where passengers were allowed off. The train was then taken out of service and brought to a maintenance facility in Boston.

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