A series of electrical circuit breakers malfunctioned and produced smoke in a Metrorail tunnel Wednesday night, forcing transit officials to suspend service near the Pentagon City station.

No fire was reported and only a light amount of smoke was detected in the tunnel just before 10 p.m., said Sherry Ly, a Metro spokeswoman. No injuries were reported.

Metro officials shut down rail service for about 30 minutes and used buses to shuttle passengers between the Pentagon and Crystal City stations, and later ran trains on a single track as the Arlington fire department investigated, Ly said.

The cause of the malfunction was not immediately known.