A gas explosion triggered a major fire in the unincorporated community of Ashland near Hayward on Thursday after an underground line was damaged by a construction crew, fire officials said. At least one home was destroyed, windows were blown out and nearby houses shook.Six people were taken to hospital for treatment, Alameda County Deputy Fire Chief Ryan Nishimoto said. Three were sent immediately with serious injuries and three others had more minor injuries, AP news agency reported.Three structures on two separate lots were severely damaged, Nishimoto said. Some of the 75 firefighters on the scene were forced to back off momentarily after feeling electric shocks from fallen power lines.The video, which came from doorbell camera footage, showed a large building engulfed in flames and debris scattered across the area. “We were sitting in the house and it just … everything shook. Stuff fell off the walls and when we looked at the camera it was like you were watching a war video,” said Brittany Maldonado, who lives across the street and provided the Nest doorbell cam footage to ABC7 News.The National Transportation Safety Board said Thursday it was sending a team to investigate. Pacific Gas & Electric Co was alerted at 7:35 a.m. that a construction crew not affiliated with the utility had damaged an underground gas line. Utility crews arrived to isolate the damaged line but gas was leaking from multiple locations. Workers stopped the flow of gas at 9:25 a.m., and the explosion soon followed.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.The explosion occurred in Ashland, near the city of Hayward in the East Bay, about 15 miles south of Oakland. Hayward is home to about 160,000 residents.Sirens were heard as police arrived and flames spread at the site of the collapsed building. Several workers lifted a large piece of debris near an excavator that was digging in front of the home just before the blast.Rebecca Boone in Boise, Idaho, Julie Watson in San Diego and Christopher Weber in Los Angeles contributed to this report.

