The building where the apparent natural gas blast occurred shortly after 11 a.m. EDT was undergoing renovations, Philly.com reported.
Two other homes were damaged, the news website said, and the explosion led to the evacuation of up to 25 people from the vicinity.
The incident, which occurred in the 400 block of Daly Street in South Philadelphia, left a worker in the basement of building hospitalized in critical condition, KYW-TV, Philadelphia, reported.
Neighbors said they hear a loud rumble, and noticed a strong odor of gas, shortly after the collapse.
Police evacuated neighboring homes, and shut down the neighborhood as a precaution, KYW-TV added.
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