FOREST HILLS (KDKA) — A duplex caught fire after an explosion in Forest Hills Sunday afternoon.

According to the official Allegheny County Twitter account, emergency crews were on the scene of a fire in the 320 block of Avenue A in Forest Hills after a duplex explosion.

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It happened around 1:30 p.m.

“It sounded like when a dump truck’s door slams, and you saw the front of the building explode out into the street and the back half fell after that,” said witness Victor Romanovich. “The windows from everything flew out into the street.”

There were reports that the fire spread to the basement of the other half of the duplex.

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No one was inside at the time of the explosion and following fire. One firefighter was injured while battling the flames.

Investigators are working to determine what caused the fire. Representatives from Peoples Natural Gas were also on scene.

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