The fire broke out around 10 p.m. Thursday on George Street in Paterson at a three-story factory primarily occupied by Skorr Products, which makes equipment for caterers.
The flames quickly spread to five alarms and raged out of control for hours.
Windows around the factory were exploding from the intense heat and pressure.
Firefighters also had to battle the cold weather and freezing water in addition to the flames.
"We saw flames shooting through the roof, a couple explosions, it was roaring for awhile," Nutley volunteer firefighter Mike Lumberto said. "It was loud. It was really rumbly, too. It was coming from the roof, coming out the windows. Couple windows exploded. It was an experience."
Smoke could be seen for miles, and mutual aid from surrounding towns rushed to the scene.
No injuries were reported.