They expected to have the fire 100 percent contained by Monday afternoon.
The flames broke out around 10:00 a.m. Sunday near the border of Camden and Burlington counties.
Smoke plumed above nearby Atsion Lake shortly after fire crews made the discovery.
It proved to be another long night for firefighters who had already fought several other stubborn blazes in Cumberland, Salem, Gloucester and Ocean counties.
"It's been some extreme fire conditions due to the dry weather we've had, debris and windy days," said Billy Behnke, New Jersey Fire Service.
Officials say no homes were threatened but access to some roads was blocked to the public. Campers were also forced to evacuate.
Firefighters were warning residents in nearby townships that they could expect to see smoke on Monday morning.
Notifications were made about the smoke through reverse 911 calls.