Montgomery County Fire and Rescue shut down the northbound and southbound lanes of Interstate 270 in Clarksburg, Md., because of a broken gas main.
A construction crew was digging at the end of the exit ramp from I-270 to Clarksburg Road and struck the 6-inch main, Montgomery County Fire and Rescue Assistant Chief Scott Graham said.
"This is a pretty significant main, a pretty significant size," Graham said.
I-270 was closed between Father Hurley Boulevard and Route 109. Clarksburg Road is shut down in both directions between Whelan Lane and Route 355.
Raw Video: Clarksburg Gas Leak
Fire and rescue said I-270 would reopen at about 10 p.m., but Clarksburg Road and the ramps to Clarksburg will remain closed overnight.
Washington Gas went to the scene. A lot of gas was being released -- the pressure from the gas was blowing puffs of dirt out of the hole -- but the 8 mph breeze is helping dissipate it, Graham said.
The priority was to make sure Washington Gas and Fire and Rescue safely fix the leak, Graham said.
There are homes about 1,000 yards from the leak, and the fire department is monitoring the atmosphere around the homes and businesses in the area. Nobody has been evacuated.
Washington Gas customers in the area will notice a disruption in service.
Stay with NBC Washington for updates as they become available.