The MBTA pulled all of its new Orange and Red Line cars from service this week, after one of the cars experienced a battery failure Monday morning.
A spokesperson for the T said the car was not in service at the time, and that engineers and technicians were working to determine the cause of the failure.
The decision came on the same day legislative leaders announced they will hold an oversight hearing in the coming weeks to look at problems with the T.
Federal transit officials also are conducting a review of the transit agency. An initial report out last week identified a number of safety concerns.