Nassau fire marshal Michael Mennello was on the phone Wednesday night, explaining to a homeowner why her Lake Success house had caught fire the night before, when he heard a call over the radio: The house was on fire again.

"I said, 'You better just meet me at the house,' " Mennello said Thursday.

Both fires at the $1 million, unoccupied two-story home were deemed accidental and appeared to be related to construction work, Mennello said. No one was hurt in either fire.

The first fire, on Tuesday night, started when polyurethane fumes from a freshly coated wood floor were ignited by an air-conditioning system, Mennello said.

The second fire, on Wednesday night, was caused when of plastic bags filled with sawdust spontaneously combusted, he said.

The home was sold earlier this year for $1.145 million to a Great Neck man. He could not be reached for comment Thursday.

The Tuesday fire caused extensive damage to the attic and roof, Mennello said. Manhasset-Lakeville firefighters needed an hour to put out the fire, Mennello said.

Fumes on the first floor were sucked into the central air-conditioning, then ignited in an air handler in the attic, he said.

The Wednesday night fire caused less damage and was doused in about 20 minutes, he said.

That fire was caused by a buildup of heat in the bags caused by decomposing wood shavings, moisture from water used to put out the Tuesday fire and high heat, Mennello said.

"The temperature in the home was elevated" because of the first fire, he said.