Also still hospitalized last night were a 23-year-old woman and a 13-year-old girl, both in stable condition at Temple and St. Christopher's Hospital for Children, respectively, Small said.
The other seven people were treated at city hospitals and released.
Officials said the fiery blast was caused by an industrial-size propane tank, which exploded about 5:30 p.m. from the back of La Parrillada Chapina, a food truck run by a hardworking Guatemalan family.
The 4-foot tank burst violently, sailing 150 feet across Wyoming Avenue, Small said.
It landed in the 14-year-old boy's back yard, startling him as he was chowing down on noodles in his bedroom.
"It's really terrible; I never imagined this could happen," said the teen, whose name is Jimmy. His last name is being withheld at his father's request.
Surveillance footage viewed by the Daily News shows a spectacular explosion:
In one frame, the truck is parked, its owners whipping up their food. A split second later it is swallowed up by a massive fireball, spewing flaming tendrils that span Wyoming Avenue and ignite a utility pole on the opposite side of the street.
After the initial blast, Jimmy ran to his window, watching as the blaze roiled the truck. He spotted the 42-year-old victim lying in the street, he said, her body badly burned.
Michael Blackie was about a block away at that point, rounding the corner of Wyoming Avenue near 4th Street.
He heard a boom so loud that he initially thought an earthquake had come to Northeast Philly.
"It sounded like a bus blew up," said Blackie, who lives about a block away on Mentor Street.
When he stepped onto Wyoming, he came upon the same scene Jimmy described: A woman, seemingly blown from the truck, was lying in the street.
She was, in Blackie's words, "smoldering, like something out of 'CSI.' "
Blackie said the woman, whom a family member identified as Olga, is a hardworking mom whose truck has been a fixture in the neighborhood for years.
"I feel sad for them, sad for the situation," Blackie said. "They're an independent business . . . how do you recover from something like this?"
He said the aftermath of the explosion was "chaotic," with bystanders screaming and running, and SEPTA transit cops trying to retain order. The transit authority has an office a few yards from where the truck was parked, and its officers were first on the scene.
They were quickly joined by city cops and Fire Department personnel, who remained late last night as the investigation into the explosion continued.
Romelia Reyes watched them work from her porch, cordoned off by crime-scene tape at 4th Street and Wyoming Avenue.
She was inside her house when the tank blew up, and described the violent noise it made as "horrible."
"I've seen a lot on this block," she said in Spanish with the help of her English-speaking daughter, "but this was scary."
Another Feltonville horror: "They used to hear her scream."
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