Supposedly sealed building caught fire

From the Queens Gazette:

Fire marshals are looking into the cause of a stubborn, smoky fire on the afternoon of June 10 that destroyed a vacant home on 47th Street in Astoria, fire officials said.

Twenty-five fire units and 106 firefighters responded at about 4:30 p.m. to the two-alarm blaze at 31-40 47th Street that sent one firefighter to Mount Sinai Queens with burn injuries, a fire spokesperson said. Several other firefighters were treated for smoke inhalation and other injuries at the scene.

Fire marshals arrived at the scene a short while before the blaze was brought under control, to begin combing through the remains of the building to determine exactly what sparked the fire. Fire officials would not say if the blaze is considered suspicious.

I think I have the answer: