MCFRS personnel responded to the incident at about 3:15 p.m. in the 6500 block of 78th Street in Glen Echo, a block from a popular shopping center on MacArthur Boulevard.
MCFRS spokesperson Pete Piringer tweeted that the leak was under control as of 3:35 p.m. but some neighborhood streets might remain closed. There were no injuries or illnesses reported.
The leak apparently stemmed from an excavation site on 78th Street. Firefighters are continuing to check homes for higher-than-usual gas levels.
Some evacuees were led to a nearby church.