The sun was peaking over a freezing-cold South Philadelphia when they heard the boom.

The 1400 block of South Eighth Street was on fire just before noon Thursday, after an explosion ripped through a rowhouse on the residential street, blowing out windows and shaking homes. Neighbors screamed, “We need a fire extinguisher!” and ran toward the blaze, only to find someone trapped under the debris.

» UPDATE: Woman fears father dead as hazardous conditions at South Philly explosion scene hinder recovery efforts

They couldn’t get to the person.

First responders arrived within minutes, diving into a maelstrom of fire, while live wires hung and gas leaked around them. They threw their ladders onto what had become a pile of bricks and started crawling. But then, the house next door crumbled.

A person trapped in one of those adjacent houses is presumed dead. So is the person the neighbors tried to save.

“We saw her feet," said Lisa Marie Cerra, who lives on the block. "And then they couldn’t get to her.”

It’s not clear what caused the explosion that collapsed three homes and left two others with significant structural damage.

As the sun set Thursday, as firefighters were still spraying water onto the collapsed houses, the window of opportunity to safely rescue people closed. Recovery efforts were too dangerous to carry out in the dark, so they will begin Friday morning.

“This is a real punch in the gut for our [first responders, who] really thought they were going to be able to make a rescue,” Fire Commissioner Adam Thiel said. “They’re struggling with that outcome, as we all are.”

About 60 people were evacuated and 10 houses won’t have utility service for the night.

It took firefighters more than three hours to control the three-alarm blaze, which they battled from the street and adjoining rooftops. Onlookers cried as they watched the homes burn. A woman was carried from the scene, and neighbors whispered that her son was trapped inside.

Thursday night, as temperatures dipped, firefighters shepherded in heavy equipment with extreme care — as a sinkhole was forming under the street.

“It was a Herculean effort,” said Ray Vozzelli, a retired Fire Department lieutenant who was on the scene. “They tried their best.” No first responders were injured in the process.

It was just after 11:30 a.m. when dispatchers began receiving calls from people who had heard an explosion and smelled gas in this residential area of decades-old, two- and three-story brick houses. Thick black smoke was billowing and could be seen miles away, while bright orange flames shot into the air.

Locator map of a home explosion in South Philadelphia.

Vinny Termini, co-owner of longtime neighborhood staple Termini Bros. Bakery, about a block away from the explosion, said he heard a loud boom and walked down the street with neighbors toward the building.

“Some neighbors were in the rubble looking for people," Termini said. "It was upsetting, very upsetting.”

Jennifer Romaniello, who lives across the street from where the explosion took place, said it felt like someone had dropped a bomb.

“I thought the terrorists had come,” she said.

Jeffrey Beres, general manager at Geno’s Steaks a few blocks away, said he was working in an upstairs office when “it felt like a three-ton air-conditioning compressor fell on the roof."

“I looked at the monitor to see if a car had run into the side of our building,” Beres said, "because the whole building shook.”

Firefighters attempt to extinguish a house fire at the intersection of Wilder Street and 8th Street.
Anthony Pezzotti
Firefighters attempt to extinguish a house fire at the intersection of Wilder Street and 8th Street.

Dozens of first responders arrived on the scene, including more than 120 members of the Fire Department, to battle the blaze and help evacuate residents. SEPTA buses were used to keep residents and firefighters warm on a day when temperatures didn’t get out of the 20s.

Displaced residents were escorted to South Philadelphia High School, city officials said, to have a warm place to stay while the American Red Cross coordinated overnight arrangements.

Meanwhile, a lengthy investigation on the block was only beginning. While a special operations team was attempting to recover individuals trapped in the rubble, fire marshals and other investigators were working to put together the pieces.

The Philadelphia Gas Works couldn’t say if the explosion was gas-related. Officials with the Department of Licenses and Inspections and the Office of Emergency Management were on the scene, but also couldn’t provide a reason for the explosion.

Residents began to file into their nearby homes Thursday evening. Brian McQuilkin, watching from less than a block from his front door, said his neighborhood felt spooky.

“Nothing ever happens around here,” he said. "And near Christmastime.”

Sara Wachter-Boettcher’s stomach dropped when she initially heard the explosion’s boom from inside her rowhouse a block away. She walks down the street every day.

“Now I’m thinking about which people live in which house,” said Wachter-Boettcher, who has lived in her house since 2015. “It’s pretty terrifying when you think about South Philly. Who knows what kind of older gas systems, electric systems, everyone has?”

“Something like this makes you worry about the density here," she said, “and think about how it could all go down.”

Philadelphia emergency management officials warned residents to expect traffic tie-ups in the area and delays on surrounding streets.

SEPTA bus Routes 29, 47, 64 and 79 were detoured near Eighth and Reed Street while streets remain closed due to the fire, a spokesperson said.

Staff writers Joseph A. Gambardello, Caitlin McCabe, Rob Tornoe, Tommy Rowan, and Ellie Silverman contributed to this article.