By Steve Beck and Ben Simmoneau

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ALLENTOWN, Pa. (CBS) – Authorities in Allentown say four people suffered minor to moderate injuries after a gas explosion ripped apart the front porch of a home.

The explosion happened at 213 North Fulton Street just before 1 p.m. Thursday afternoon.

Fire officials say two workers for Great Western, a subcontractor for UGI, were working on the gas line that runs from the gas main into the home at the time of the explosion.

“They had class two injuries, which are moderate injuries,” said Assistant Fire Chief Lee Laubach. “One was inside; one was outside.”

Authorities say two others who live inside the home were taken to the hospital for minor injuries.

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“It rumbled a little bit, quick rumble, then was mostly a big boom,” said neighbor Aimee Vazquez, who grabbed her son and ran from the house. “I couldn’t believe it. One of the workers said he actually flew from the porch.”

A spokesman for UGI says the company is replacing all the gas lines under this block of Fulton Street because they are old and made of cast iron. The spokesman would not say if that replacement had anything to do with an enormous gas explosion just a few blocks away on 13th Street in Allentown last February. That explosion killed five people (see related story).

“I don’t think at this time we can tell definitively what caused this explosion,” said UGI spokesman Dan Adamo.

Investigators from UGI and the Pennsylvania Utility Commission were on the scene to begin the investigation. Fire officials say the home will be habitable once the front porch is reinforced and a few broken windows are replaced. Five people live there.

None of the other homes on the block had damage, although neighbors were evacuated for a time while officials tried to contain a gas leak.

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