"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.
Together, the Salindos climbed over the backyard fence to escape the heat, but not before the intense temperatures singed their skin. Ricardo suffered second degree burns on his leg and neck from the radiating temperatures, and son Richard now has burns on his arms.
With their home completely destroyed, Salindo, his wife and their son spent Thursday night in a hotel. On Friday, the father and son's arms and legs were bandaged in thick layers of white gauze, but they were still counting their blessings.
"If we'd stayed any longer in the house, we're dead," said Salinda. "We're lucky to be alive."
Maldonado said Friday that the explosion was caused by a gas pipe rupture but added, "We don't know what caused [the rupture] or what happened."
"We will find out soon," he said.
The explosion occurred just after 6:15 p.m. Thursday in a residential area near highways 280 and 380 in San Bruno, just south of San Francisco. Thirty-eight structures were completely destroyed and another seven badly damaged.
"You've heard the numbers," San Bruno mayor Jim Ruane said Friday in a news conference. "Unfortunately, the numbers are going to get higher."
Local news reports said residents had attempted to alert Pacific Gas and Electric, the company that operates the pipelines, to the smell of gas days before the explosion.
"We have records that we are going back through right this minute to try and confirm what those phone calls looked like and when they occurred," PG&E president Chris Johns said Friday. Johns said that company policy was to immediately respond if someone calls in with a complaint about the smell of gas.
"We're really saddened and sorry about this tragedy," he said.
Officials from the National Transportation Safety Board are investigating the cause of the blast and will work with PG&E to determine exactly what happened.
"I want to make sure everybody knows that we are committed to do what's right and what's appropriate to help all the families and others who have been impacted by this tragedy," Johns said.
Johns said that no PG&E crews were working in the vicinity during the explosion, but he did not know about any other construction going on. The pipe that ruptured, Johns estimated, was 40 or 50 years old.
ABC News' Ariane Nalty, Neal Karlinsky and The Associated Press contributed to this report.