BOSTON (State House News Service) – Orange Line riders should expect slow commutes with gaps of about 15 minutes between trains after the MBTA pulled nine cars from service because of unexpected “electrical arcing,” the agency announced Friday.

MBTA spokesperson Lisa Battiston said in a statement shortly before 2:30 p.m. that a T engineer “identified a failure in a power cable that may have created some electrical arcing with a nearby train axle.” Battiston said that routine inspection was “recent,” but did not specify exactly when. After examining all other Orange Line vehicles, Battiston said the MBTA identified nine cars affected by electrical arcing and removed them from service for repairs, which will include axle replacement.

A total of 11 axles across the nine cars have been affected, Battiston said. Battiston did not describe a reason for the electrical issue, saying that engineers for both the T and for Chinese firm CRRC, which manufactured the newest Orange Line trains, “continue to investigate the root cause of this condition.” The MBTA will deploy “an enhanced inspection program” until repairs are complete, she said.

“As the MBTA continues its inspections and performs necessary repairs, Orange Line riders will continue to experience longer headways of about 15 minutes between trains,” Battiston said. “The T apologizes for these inconveniences.”

The announcement came shortly after the Boston Globe reported that the T had cut Orange Line service by nearly half in recent days without notifying riders about a reason for the change. Battiston did not immediately respond to questions Friday afternoon about how many Orange Line vehicles remained in passenger service or whether the T would redeploy older vehicles, which the MBTA stopped running in the wake of a month-long maintenance shutdown this summer, to restore capacity.