The fire broke out at around midnight at a building at 119 Colt Street.
Irvington firefighters were assisted by fire companies from other towns.
At one point, fire crews were ordered off the building's roof over fears of a collapse.
The roof did later collapse, but the fire was finally declared under control at about 5 a.m.
No injuries have been reported.
There is still no word on the cause of the fire.