Metro trains were single-tracking for about 45 minutes on the Red Line between the Grosvenor and Medical Center stations Thursday morning because of an arcing insulator on one of the two tracks.
Metro said riders should expect lingering delays in both directions on the Red Line.
Pete Piringer, spokesperson for the Montgomery County Fire and Rescue Service, said firefighters arrived on the scene around 10:15 a.m. to help Metro maintenance crews investigate the arcing insulator.
Arcing insulators, in which water or other material contacting electrified rails can cause smoke or fire, are common in the Red Line tunnel near the Medical Center and Bethesda stations.
In 2017, Metro is scheduled to shut down the section of the Red Line from the Grosvenor station to Friendship Heights for 14 weekends to fix leaks in the tunnel ceiling.
