The fire broke out around 9:30 a.m. on Thursday in the 600 block of Harding Highway in Franklin Township.
Chopper 6 was over the scene as heavy smoke billowed over the trees. Fire crews were using ladder trucks to try to put the fire out.
Crews battling building fire in Franklin Twp., NJ
Authorities say they do not believe foul play was involved.
Franklin Township police in Gloucester County say a faulty part in the exterior HVAC unit at Northeast Pool Distributors caused the blaze last week.
The fire led to the evacuation of two nearby schools as a precaution.
Hazmat crews and environmental officials were also called in to monitor air quality.
No injuries have been reported.