In total, two people are presumed dead after Thursday morning's fiery explosion trapped at least one person and left at least one other person unaccounted for.
Officials said there is a possibility other people may have been walking by when the explosion occurred around 11:30 a.m. Thursday on the 1400 block of South 8th Street near Reed Street and may also be trapped in the debris.
Fire Commissioner Adam Thiel said it was too dangerous for rescuers to immediately enter the buildings and recover the victims.
"There's a lot of remaining risks. We still have buildings that are basically buildings exposed to an explosion and could collapse at any second," he said.
The cause is being investigated by local, state and federal authorities, but a source tells Action News they are looking into if an October water main break could be connected.
As for the question if there was work being done on the street, officials will only say it's early in the investigation.
Thiel spoke to reporters Friday morning. He cautioned this is a slow process and risks still remain out there including the potential for more houses being in danger.
He commended not only first responders but people in the community, as well.
"You really saw the best of Philadelphia yesterday in the wake of this tragic event where we had neighbors helping neighbors, friends helping friends, families helping families, and a lot of folks who risked their lives to try to rescue complete strangers," Thiel said.
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Kiana Thompson, the principal at the Academy at Palumbo High School, confirmed to Action News that one of her students lived at the house that exploded. That student's brother was killed.
Thompson was at school on Thursday when a man came in looking for the student.
"He said, 'I need to get a kid out early.' And I said, 'What's wrong?' He said, 'It's an emergency, the house that exploded...' I said, 'Did he live on the block or was it that house?' He said, 'It's that house.' And they both started filling up with tears," Thompson said.
While crews continued to spray hot spots in the frigid weather, Thompson said she was able to get in touch with the mother of the victim. It's a call she'll never forget.
"It wasn't very long. I didn't keep her too long. She was crying hysterically. saying, 'I don't understand. I don't understand, why did this happen? I lost my son,"' Thompson said.
Viewer video: South Philadelphia explosion, fire leaves two people trapped
Authorities responded to the scene Thursday morning after they received multiple calls about a house explosion and the smell of "possible gas."
Mike Seccia, who owns the nearby Cosmi's Deli, said the explosion was "the loudest bang he's ever heard."
He gave his customer a fire extinguisher and they headed to the scene.
"The small fire then became one of the worst spectacles I have ever seen," Seccia said.
Seccia said they saw a man caught in the rubble, but they couldn't get to him.
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Brian Contrsciane was among the neighbors who tried to help.
"There was a guy in there. It looked like he was in bed and he was basically wrapped up inside the mattress. Because so much rubble had fallen, we couldn't get leverage to pull him out. Like a minute later, the whole house collapsed. The guy's still in there," Contrsciane said.
Firefighters were there within minutes. They rushed through the flames, passing arcing wires, trying to reach the victims, but couldn't make it to them either.
"I talked to them. They wish they could have made that rescue. The reality is that was an incredibly dangerous situation and sometimes we do everything we can and it's just not enough," Thiel said Thursday.
Philadelphia fire commissioner provides update on house explosion
Three rowhomes fully collapsed due to the explosion and two more were seriously damaged.
A second-alarm was struck bringing more than 100 Philadelphia firefighters to the scene.
Dozens were evacuated from nearby homes. Crews turned off power and gas in the neighborhood. It is not known when they will be allowed back to their homes, or when power will be restored.
Anyone who is affected by the explosion and needs shelter should call 1-800-RED-CROSS.
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The explosion compromised the road and now there is concern of a sinkhole forming.
On Friday morning there was still a lot of debris and structural instability, a too dangerous scenario for firefighters to go in and extricate the two people believed to be trapped.