(CNN) -- Row houses were reduced to rubble when an apparent explosion rocked a Philadelphia neighborhood Monday, sending at least eight people to hospitals.
Witnesses told CNN affiliate KYW that they smelled gas after the blast.
"I was sitting in the house and I heard a big bang," Mike McGraw told KYW. "The door slammed and the TV went out."
His son, Mike McGraw Jr., said he saw the buckled buildings and watched firefighters hose down a man who had been burned.
"They threw this baby out the window because the girl was on fire, and the fireman had to catch the baby," he said.
A contractor was doing rehab work in a vacant home when it collapsed, Deputy Fire Chief Robert Coyne told reporters. The two adjacent houses were also destroyed, he said.
Coyne said authorities were still investigating what caused the homes to collapse, but it appeared that there was an explosion.
One person was in critical condition, Coyne said, and 25 people had been evacuated from the south Philadelphia neighborhood.
Aerial footage of the scene showed a large pile of rubble between two buildings.
Last month, a four-story wall of a vacant building in Philadelphia collapsed onto an adjacent Salvation Army thrift store, killing six people and injuring 13.
Authorities charged crane operator Sean Benschop, 42, with involuntary manslaughter and other related charges.
CNN's Melanie Whitley and Sarah Hoye contributed to this report.
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