ONE OF THE MBTA’S new Orange Line trains became disabled when it experienced a problem with one of its braking units on Thursday, prompting the transit authority to remove all other new Orange Line trains from service until the cause of the problem is determined.

“With safety being the top priority, the MBTA took this action out of an abundance of caution,” the T said in a statement, which noted the brake problem “never presented a hazard for riders nor employees.”

The statement said Orange Line service will continue with older trains but wait times are likely to increase from 7 minutes to 8.5 minutes.

The T currently has a total of 64 new Orange Line cars and six new Red Line cars available for service.

The decision to pull all of the new Orange Line trains from service came as the Federal Transit Administration has assumed a “safety oversight role” at the agency. MBTA officials earlier in the week said FTA officials arrived on site last week and will remain for several weeks.

An MBTA spokesman also provided additional information on three tool cart derailments during the laying of 1,800 feet of track on the Blue Line. The spokesman said two of the derailments occurred before new track was aligned in its final permanent position. The cause of the third derailment was still being investigated, the spokesman said.

The derailments extended the construction period on the Blue Line by about a week and a half. The T said on Thursday it was tracking the costs related to the extended Blue Line shutdown and reviewing the terms of its contract with the contractor.

“The MBTA will pursue all available remedies after a full accounting of the costs and completion of its contract review,” the spokesman said.