City firefighters had to cut a fence behind the Main Street apartments and enter the property through the Target parking lot to conduct searches and ventilate the roof after the blaze broke out around 1:15 a.m.
Firefighters extinguished heavy flames that shot out the window on the first floor and extended to the second.
The two-alarm fire was knocked down within 25 minutes and declared under control within an hour.
Three minor injuries were reported, including one involving a firefighter who responders said had difficulty breathing.
Hackensack Volunteer Ambulance Corps, and BLS and ALS units from Hackensack University Medical Center responded.
Firefighters from Bogota, Englewood, Ridgefield Park, Hasbrouck Heights, Little Ferry, Maywood, River Edge and Teaneck assisted their Hackensack colleagues either at the scene or in coverage.
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