Two major Metrorail stations on Washington D.C.'s Red Line were closed Wednesday morning as officials investigated reports of smoke.

Officials closed the Gallery Place-Chinatown and the Metro Center stations at about 10 a.m. after hearing reports of smoke between the two stations. The cause of the smoke has not been determined and passengers are being allowed to leave the station, but all Red Line trains are terminating at the Farragut North station and the Judiciary Square station, with shuttle bus service in effect.

Yellow and Green Line trains are continuing to pass through the Gallery Place-Chinatown station and Blue and Orange Line trains are continuing to pass through the Metro Center station. 

Update: Officials have since reopened both stations and determined that the smoke was being caused by a collection of smoking debris in a vent shaft between the two stations along the Red Line.

—This post was modified at 12:03 pm.