PG&E received word at 4:37 a.m. that a third-party construction crew had ruptured a gas line at 1354 Burlingame Ave., PG&E spokesman J.D. Guidi said.
Crews responded and found that the line affected is a 4-inch plastic main, he said.
As of 8 a.m., crews were doing excavation to reach the line and cap the leak. They hope to have the leak capped by 10 a.m.
Burlingame police Sgt. Don Shepley said businesses have been affected, but he did not know how many. He said the hope is that the leak will be capped by the time most businesses are scheduled to open for the day.
Burlingame Avenue is closed between El Camino Real and Park Road, and Primrose Road is closed between Donnelly Avenue and City Hall Lane, Shepley said.
No cars or pedestrians are being allowed into the area, and Shepley said there have been reports of natural gas odors as far east as Washington Park.