New Jersey State Police responded to the scene around 10:00 a.m. Tuesday in the area on milepost 63, near the Route 33 Exit in Hamilton Township.
The truck pulled to the side of the road and dumped the hay. Emergency crews then arrived on the scene and doused the hay with water.
No one was injured in the incident.
It is unclear what sparked the fire.
The scene is now clear and traffic is flowing normally.
