The incident happened in Roselle where everyone who lives in the building escaped unharmed.
Fire officials say the fire appears to be an accident, causing a partial roof collapse and floor collapse on the fourth floor.
One firefighter and two captains have minor injuries from burns and smoke inhalation.
The fire drew several fire departments from across Union County with more than 97 firefighters on the scene.
Fire officials say it was especially difficult to put out because the building is old and did not have sprinklers.
Red Cross New Jersey is assisting a total of 16 families (37 residents) affected by the fire.
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