The fire was reported at 162 Mapes Avenue around 1:50 a.m., Newark Public Safety Director Brian A. O’Hara said in a release.
About 70 firefighters responded to the blaze, which had extended to the roof and was later upgraded to a second-alarm, O’Hara said.
The fire was placed under control just after 3:40 a.m.
Meanwhile, one firefighter was taken to University Hospital for heat exhaustion and four others for smoke inhalation, O’Hara said.
A total of 18 families including 21 adults and a child were relocated, authorities said.
The cause of the fire remains under investigation by the Newark Department of Public Safety’s Arson Unit.
Click here to follow Daily Voice Union and receive free news updates.