Fire investigators are looking into whether fuel or accelerant was behind the explosion in Borough Park on Saturday despite previous statements that natural gas may have been involved.

Fire Commissioner Daniel Nigro said Thursday that "there was no natural gas flowing to the second-floor apartment since June 26" and that "no significant natural gas flow into any part of the building had occurred" before the explosion.

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Over the weekend, officials assumed the blast was set off by a gas leak after learning that a tenant on the second floor appeared to have moved a kitchen stove out of the apartment and may have left the gas connection open.

The new information that no gas was flowing into the building for more weeks has led investigators to question if an accelerant of some kind might have been used.

On Monday, authorities said they recovered the remains of a second person from the rubble of the blown out building.

Officials have declined to confirm whether the remains were of Francisca Figueroa, whose family said has not been heard of since the day of the explosion.

Ligia Puello, 64, died after the explosion and was found in the building's stairwell. She lived on the third floor.