Workers have capped a gas leak in San Bruno that shut down commuter train service in two directions.
California highway officials have closed Highway 99 in both directions just south of Madera due to a gas main rupture.
Some streets in Concord were shut down Tuesday morning because of a gas leak, which has also prompted the closure of state Highway 4 off-ramps, police and the California Highway Patrol said.
Firefighters and PG&E crews were on the scene of a gas leak caused by a hit-and-run car crash in San Jose that prompted the evacuation of neighboring homes in the area, a fire captain said.
Records show Pacific Gas & Electric, whose pipeline exploded in San Bruno earlier this month, has reported gas line leaks at a rate six times the average for other large pipeline operators.
Corrosive microbe gases are being investigated as a possible cause of the San Bruno natural gas pipeline explosion that killed seven people and destroyed 37 homes this month.