Updated at 11:20 a.m.
Metro said it is back to normal service on the Green and Yellow lines after an earlier problem with a defective stud bolt on a track near the Gallery Place station.
The problem caused service to be suspended on part of the two lines. No one was hurt in the incident, but there was some smoke, officials said.
Riders may experience minor delays as the trains return to normal service.
Original post at 11 a.m.
Rail service on the two lines is suspended between the Mount Vernon Square and L’Enfant Plaza stations because of fire department activity at Gallery Place.
Shuttle buses are available to replace trains. It is unknown how long the service will be suspended.