PHILADELPHIA (CBS) – While three Philadelphia Gas Works employees remained in critical but stable condition in Temple University Hospital with injuries suffered in Tuesday’s night explosion and fire in the Tacony section of the city that killed one of their colleagues (see related story), authorities are now focusing on what caused it.

PGW spokesman Doug Oliver says the Philadelphia fire marshal is leading the investigation and the natural gas utility is assisting.

Oliver says PGW crews responded quickly once summoned by fire crews on the scene.  He says they found a 12-inch high-pressure main running under Torresdale Avenue had apparently sprung a leak and were trying to isolate it at a nearby property when the explosion occurred.

About an hour before, Dr. Edward Genovesi had just locked up his chiropractor’s office at the corner of Torresdale Avenue and Disston Street, when he first spotted the gas leak. It was about 7:15. He says he could see gas bubbling in puddles of water.

“I looked closer, and it was gas that was coming out so rapidly,” he said. “Bubbling up out near the sewer, out of the concrete.”

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He called 911 and got one of his upstairs tenants, Jim McNichol, out of the building. The explosion destroyed Dr. Genovesi’s office and the two apartments above.

I lost “everything that I have,” said McNichol. “My car was parked out there, that blew up. Car, apartment, everything.”

Oliver says one avenue that investigators will take is the impact of the cold weather on the main beneath the street.

“As the ground freezes and thaws and freezes and thaws, you have expanding and contracting, expanding and contracting, which sometimes on an older system could cause leaks,” Oliver explained.

Oliver says several state and federal agencies are being kept in the loop on the probe, as well as the mayor, City Council, and the Philadelphia Gas Commission.

Reported by Mark Abrams, KYW Newsradio; Ben Simmoneau, CBS 3

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