BOSTON (AP) — Massachusetts transit investigators looking into a runaway train are recommending that the operator be fired even as a lawyer for the driver said he denies tying a rope or cord around the train's throttle to force it open, as authorities have suggested.

Transit investigators recommended Tuesday that the operator, 53-year-old David Vazquez, be fired. The recommendation came after a disciplinary hearing.

Massachusetts Bay Transportation Authority General Manager Frank DePaola was expected to accept that recommendation, according to an individual with direct knowledge of the decision. The person wasn't authorized to discuss the situation and spoke to The Associated Press on condition of anonymity.

The driverless train left a suburban Boston station Thursday morning and rumbled through several stops before transit workers stopped it by cutting power to the rails. No passengers were injured.

Philip Gordon, a lawyer representing Vazquez said he hopes the MBTA will continue its investigation into what happened, including looking carefully at the train itself.

"Mr. Vazquez has categorically denied tying a rope or cord around the throttle or brake system," Gordon said Tuesday in a phone interview.

Gordon also said the protocol that requires a train's only operator to get off the train to throw a switch in certain situations raises safety concerns for drivers and passengers.

Transit officials have said the operator, identified as Vazquez, got off the train to put it into "bypass mode" after receiving permission to override a signal problem. He suffered a minor injury when he was brushed by the train as it moved away from the station.

Secretary of Transportation Stephanie Pollack said Friday the train's emergency brake hadn't been engaged and that investigators were also looking at whether the train's throttle had been tied back with a cord — meaning the train would start moving as soon as it was placed in bypass mode.

Pollack has said the only way a train could move on its own after being placed in bypass mode — absent a mechanical failure — was if the hand brake hadn't been engaged and the throttle was somehow forced into the position needed to accelerate the train.

Gov. Charlie Baker has said the operator appeared to violate several safety procedures.

Baker said Tuesday he wasn't in the disciplinary hearing and hadn't yet read the investigative report but was glad that the inquiry was moving quickly.

"For me the most important thing was that they move quickly on this to create some closure and some clarity so I'm glad that they did," Baker said.

The hearing was originally scheduled for Monday, but Vazquez failed to appear. Gordon said his client was unable to attend because of a stress-related illness.

He said Vazquez had a long record of safely driving trains and cares about his passengers.

The train carrying about 50 passengers left the Braintree station on Thursday shortly after 6 a.m. and passed through several stops before the power was gradually cut to the electrified third rail.

Transit workers first had to make sure that other trains were safely out of the way.

Transportation officials said train operators will no longer be allowed to use the bypass procedure without a second senior MBTA official present.