Flames met responding firefighters in the stairwell and knee walls of the Romano Drive home's second floor around 10 p.m., the department said.
They quickly knocked down the main body of fire, then needed to do extensive overhaul to extinguish any remaining pockets, officials said.
Tenafly, Bergenfield and Cresskill firefighters also responded, while those from New Milford and Haworth stood by at Dumont firehouses.
The Dumont Ambulance Corps also responded.
No injuries were reported, and the scene was cleared in about three hours, officials said.
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