ASHLAND — A natural gas line accidentally cut Thursday morning — and in the process of being repaired by utility crews for about two hours — instead violently exploded, hospitalizing six people and causing a fire in a quiet neighborhood near Hayward.

The blast happened about 9:38 a.m. in the 800 block of East Lewelling Boulevard in the Ashland area of Alameda County, Alameda County Deputy Fire Chief Ryan Nishimoto said.

All six people who were injured were taken to the hospital by ambulance. Authorities did not have an update on their conditions Thursday afternoon.

Two other people were missing hours after the explosion and fires, but authorities later said that they had been accounted for.

A door-camera video shared by neighbors with television stations showed digging equipment working in front of a home seconds before a massive explosion wrecks a large portion of the structure, sending at least one nearby worker fleeing from his truck.

Nishimoto said Thursday afternoon that crews were concentrating on fully extinguishing the blaze and monitoring it to keep it from restarting. Once they do so, crews were planning to search the area again to make sure they didn’t miss anything.

Manjinder Singh, a business owner on Lewelling Boulevard, said he had just parked when he heard the explosion.

“I could feel the sensation and vibration. It felt different; it wasn’t an earthquake,” Singh said.

He said that he also could smell the gas and that an officer told him “there’s gas over there, so don’t come. It might be dangerous for you guys.”

Deborah Omotoy, who said she lived next door to the home that exploded, said, “I couldn’t tell you what happened. I heard this loud noise and my roof fell in.”

She was not injured.

PG&E spokesperson Tamar Sarkissian said the utility became aware about 7:30 a.m. that a third-party construction crew not affiliated with a PG&E project struck an underground gas line in the area. Sarkissian said PG&E workers began to isolate the leak and identify where it came from.

PG&E crews turned off the gas to the leaking line about 9:25 a.m., she said. The explosion happened about 13 minutes later.

When asked why nearby homes had not been evacuated at the time of the explosion, Nishimoto said that evacuation orders are a collaborative decision made between PG&E and public safety agencies. Sarkissian said that further investigation would be required to determine why an evacuation order was not called earlier.

Nishimoto said that when crews arrived, they sounded a third alarm to protect other homes in the area. He said firefighters could feel electricity as they moved through one of the homes because of power lines that fell atop of it.

Two properties were affected by the fires, Nishomoto said. Three buildings had significant damage and a fourth did not appear to be damaged as badly.

Firefighters requested a drone from the Alameda County Sheriff’s Office to assist ground units in battling the blaze. Other fire agencies in Alameda County also responded.

Staff photographer Jane Tyska contributed to this report.