The fire rekindled hours later, requiring firefighters to return to fully douse it.
The blaze -- caused by a cigarette -- broke out around 11:40 a.m. at the Canterbury Village homes just off River Road, Police Detective Lt. Kevin Van Saders said.
Two firefighters were treated at the scene, while a third was taken to Holy Name Medical Center in Teaneck with injuries that weren't considered life-threatening, the lieutenant said.
A female resident also was treated at the scene, he said.
Flames destroyed the unit where the fire broke out, then quickly spread to two others, Van Saders said.
The fire was doused in roughly 90 minutes, the lieutenant said.
Fire companies from Bergenfield, Closter, Demarest, Dumont, Englewood, Hackensack, Haworth, Maywood, Oradell, Paramus, River Edge, Teaneck and Tenafly assisted their New Milford colleagues.
Basic Life Support and Advanced Life Support units from New Milford, River Edge, and Holy Name also responded, as did the New Milford Department of Public Works, New Milford Office of Emergency Management, New Milford Fire inspector and the Red Cross.
Click here to follow Daily Voice Cresskill-Closter and receive free news updates.