The blaze began at about 4 a.m. Sunday, Nov. 17 on Seaman Road in Jericho.
Responders arrived to find the home engulfed in flames from the second floor and heavy smoke throughout.
All residents made it out safely, though the family’s dog was found dead inside.
The Nassau County PD Arson Bomb Squad and the Nassau County Fire Marshal are investigating.
Firefighters from Jericho, with assistance from Syosset, Hicksville, Westbury, Plainview, Bethpage, South Farmingdale, Glenwood, and Carle Place, responded and extinguished the fire.
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