Firefighters were met by heavy flames on both floors in both wood-frame Franklin Street residences shortly before 7:30 p.m. Tuesday.
They rescued a dog who was returned to his or her owner.
The three-alarm blaze was brought under control in a little over an hour.
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Mutual aid included firefighters from Bogota, Englewood, Teaneck and Ridgefield Park, as well as ambulances from Hackensack University Medical Center, Holy Name Medical Center and Little Ferry.
The Hackensack Fire Prevention Bureau was determining the cause.
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