No serious injuries were immediately reported in the fire, which broke out on the upper floors of an attached three-story, wood-frame building and spread through the cockloft, blowing through the roof, shortly after 1 p.m.
The fire quickly went to four alarms, with three buildings involved.
Firefighters continued to keep water on the blaze four hours after it began.
At least 20 families were displaced, said the Red Cross, which was finding them food, clothing and shelter.
CHECK BACK FOR MORE DETAILS
Click here to follow Daily Voice South Passaic and receive free news updates.