A major gas leak shut down one of Maryland’s principal commuter routes during the evening rush on Monday, Montgomery County officials said.

Part of Interstate 270 in upper Montgomery was closed after a gas main six inches in diameter was severed by an accident in the Clarksburg area, said Assistant fire chief Scott Graham.

Shortly before 6 p.m., Interstate 270 was closed in both directions, according to state police, from Route 109 in the south to Farther Hurley Boulevard in the north.

It appeared that the leak may not be stopped until as late as 7:30 p.m.