A gas explosion set off a major fire in a San Francisco Bay Area neighborhood on Thursday after obliterating at least one home, blowing out windows and shaking nearby houses. Six people were taken to hospitals for injuries, fire officials said.

Alameda County Deputy Fire Chief Ryan Nishimoto said he did not know if those injured were workers or residents, but he said three people were immediately sent to a hospital due to their injuries and three others who were sent had more minor injuries.

Three structures on two separate lots were severely damaged, said Alameda County Deputy Fire Chief Ryan Nishimoto. Some of the 75 firefighters who responded had to back off momentarily when they felt electric shocks from power lines that had fallen on the site.

The neighborhood of single-level homes with tidy small lawns and some businesses near two freeways had been undergoing construction work for wider sidewalks and bike lanes.

The explosion occurred in the unincorporated community of Ashland, near the city of Hayward. The city is home to about 160,000 residents in the East Bay, 15 miles (24 km) south of Oakland.

Pacific Gas & Electric Co. was alerted around 7:35 a.m. that a construction crew — not with the utility — had damaged an underground gas line. Utility workers arrived to isolate the damaged line, but gas was leaking from various locations.

Workers stopped the flow of gas at 9:25 a.m., and the explosion followed shortly afterward.

Gas was flowing for two hours but the explosion happened 10 minutes after the line was shut off, PG&E spokesperson Tamar Sarkissian confirmed. She said it took time to isolate the line and stop the flow of gas.

AP video by Terry Chea & Godofredo Vasquez.