An explosion and fire near Hayward and Interstate Highway 238 injured multiple people and destroyed or damaged at least three structures, authorities said.

The incident happened on East Lewelling Boulevard just west of Mission Boulevard and south of Highway 238 in the unincorporated community of Ashland. The area has a mix of commercial and residential structures, including single-family homes.

A view from above the fire showed widespread debris scattered around the fire area. At least two of the structures destroyed appeared to be contained on the same lot of 867 E. Lewelling Boulevard, listed on Redfin as a four-bedroom, 3,957 square-foot home.

Pacific Gas and Electric said at 7:35 a.m., it was notified that a third-party construction crew had damaged an underground gas line while digging on Lewelling Boulevard, and it dispatched crews to the scene. According to PG&E, its workers isolated the damaged line and stopped the flow of gas by 9:25 a.m., but gas had been released at multiple locations, and at 9:35 a.m., the explosion happened.

Security camera video from a neighbor across the street showed construction vehicles in front of the address as a large explosion destroyed much of the main structure.

A spokesperson for Alameda County said Redgwick Construction of Oakland is currently working on a project to improve E. Lewelling Boulevard in the area, and the firm lists the project on its website. Documents from the county indicate the work involves new sidewalks, bikeways, and pavement improvements. 

CBS News Bay Area has reached out to Redgwick Construction for comment.

Alameda County Fire Department Deputy Chief Ryan Nishimoto said at least three buildings on two properties were "significantly damaged," and a third property adjacent to the other properties had minor to major damage on the side where the explosion occurred.

"Two of the three buildings look like residential structures, the one in the back of one of the properties looks like a workshop with maybe a living quarters on top," Nishimoto said. 

Six patients were taken to nearby hospitals, Nishimoto said. CBS News has learned that at least three patients were being treated at Eden Medical Center in Castro Valley with injuries described as serious.

Eight engines and two ladder trucks responded to the three-alarm fire, said Fire Department spokesperson Cheryl Hurd.

Alameda County Sheriff's Sgt. Roberto Morales said deputies were dispatched to evacuate other residents in the area. It was unclear how many residents were evacuated.

The California Highway Patrol said southbound Highway 238 to East 14th Street and Lewelling Boulevard from Mission to Paradise boulevards were shut down due to the fire, and people were being urged to avoid the area. The estimated time of reopening was not known.  

This is a breaking news update. More information to be added as available.