A city councilman says a contractor's cigarette caused a gas explosion that leveled a Philadelphia home, injuring eight people.

South Philadelphia row home collapse (WPVI TV via Facebook)

Inspectors at the scene of Monday's explosion concluded a gas leak was to blame for leveling the unoccupied home, which was being remodeled. On Tuesday, they returned as they try to figure out what caused the leak.

Councilman Mark Squilla was at the scene and told reporters that a contractor had been trying to light the pilot on a water heater. At one point, Squilla says, the man lit a cigarette and the house exploded.

The contractor remains in critical condition with burns. Seven others were treated for minor injuries.

The explosion comes less than two months after a collapse that killed six people at a downtown demolition site.

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