Gas explosion rips through home in SF’s Bernal Heights

An explosion ripped through a residence in the Bernal Heights neighborhood of San Francisco Monday morning, just as firefighters arrived on scene to investigate reports of a gas leak, authorities said.

The explosion happened at 10:14 a.m. in the 3900 block of Mission Street, near St. Mary’s Avenue.

No one was injured in the blast that shattered the second-story windows of a residential building and blew the garage door off its hinges and into the street.

Andrea Menniti, a spokesperson for Pacific Gas and Electric Co., said that the gas flow was turned off around 1 p.m. Menniti said that the three-hour delay was because crews had to drill through the road to safely access the leaking pipe, while two off-site valves also had to be shut down.

Battalion Chief Rex Hale of the San Francisco Fire Department said the explosion occurred shortly after firefighters arrived to investigate reports of a gas leak. Hale said no one was at the address when the explosion hit.

San Francisco Fire Department officials said a gas leak caused an explosion on Monday morning at a home in the 3800 block of Mission Street in the Bernal Heights neighborhood. Image captured from KTVU's helicopter. less San Francisco Fire Department officials said a gas leak caused an explosion on Monday morning at a home in the 3800 block of Mission Street in the Bernal Heights neighborhood. Image captured from KTVU's ... more Photo: KTVU Photo: KTVU Image 1 of / 7 Caption Close Gas explosion rips through home in SF’s Bernal Heights 1 / 7 Back to Gallery

The blast occurred in the garage of a three-story residential structure at 3987 Mission St., officials said.

About 19 residences on Mission Street, College Terrace and Bosworth Street were evacuated and some streets were blocked off. Residents were allowed back into their homes around 3:30 p.m.

Crews from PG&E and the city Department of Building Inspection were investigating the cause of the explosion.

“It appears that gas filled up that garage and hit a pilot light and caused the explosion,” Hale said.

A total of 470 customers were affected by the explosion, Menniti said, and about 120 customers will remain without gas while repairs and the investigation continue. As residents are allowed back into their homes, Menniti said customers should call PG&E to have their pilot lights relit.

PG&E last surveyed the affected area for potential leaks on Sept. 15 and found none, Menniti said.

Annie Ma is a San Francisco Chronicle staff writer. Email: ama@sfchronicle.com Twitter: @anniema15