"We're going to push for robust inspections and action on these pipelines, particularly the ones that are close to residential homes," the Democrat said. "I am calling on all responsible parties -- PG&E and all the regulators, federal and state -- to outline a robust inspection system that begins right now."
Acting Gov. Abel Maldonado and Boxer said they planned to hold a news conference focusing on the recovery phase and how the federal, state and city governments will help those in need of assistance.
"The community of San Bruno needs answers. The people of California need answers," Maldonaldo said. "We need to know why this happened and we need to know how this happened."
The San Mateo County Coroner's Office released the names of three of the at least four people who were killed: Jacqueline Greig, 44, a California Public Utilities Commission employee; her 13-year-old daughter, Janessa Grieg; and 20-year-old Jessica Morales.
The name of the fourth victim has not yet been released, but Faye Wharton told ABC San Francisco station KGO-TV that the body of her 80-year-old grandmother was found in the ruins of her home, which is right next to the explosion.
Wharton told KGO-TV that she received word from authorities late Friday night. She said her two aunts and uncle, who were also in the house, made it out alive, but were severely burned.
Many residents were just sitting down to dinner Thursday when they heard the explosion and felt its force. At first, many thought a plane had gone down in the neighborhood, which is just a few miles from San Francisco International Airport.
"The house started shaking much more violently than it did in '89," during the Loma Prieta earthquake, said resident Rick Bruce.
"I was in the garage, the first thing I heard was a rumble, then all of the sudden a big explosion, like BOOM," said Larry Fioranelli, who lives a block from the center of the explosion. "The heat shot up the street and into the garage... It's like a movie when you see the A-bomb explosion... You felt the concussion."
The blast shot a fireball into the air that consumed several homes in an instant. Fire reached up to 100 feet high, witnesses said. The explosion left a 15-foot crater at its epicenter.
Temperatures from the fire were so extreme that as the first fire truck got to the scene, its windshield cracked and firemen saw paint bubbling up on cars, one fire official said.
"It was like, picture a hot air balloon of fire. That big and high," Fioranelli said. Though the Fioranellis' home was undamaged in the initial fireball, they do not know if the fire reached it after they evacuated.
As many as 100 people were evacuated from their homes, though only a few dozen needed shelter Thursday night, according to Red Cross officials.
One of the homes destroyed belonged to Ricardo Salinda. He and his young son Richard were in their house when the explosion rocked the neighborhood and a ball of fire lit up the sky.
"We tried to get out of the front door, but the heat was too much," Salinda said.
Salidna quickly led his son out the back of the home, with only his wallet in his pocket. The father and son didn't even have shoes on their feet.