Illawarra Rural Fire Service superintendent Richard Cotterill said RFS and Fire and Rescue NSW crews responded to a number of triple-o calls about 10am.

He said crews first tried to reach the fire from the southern entrance to Mount Ousley, but heavy traffic made this difficult.

A fire truck was then sent from Bulli, which arrived at the blaze from the north.

"Units from Fire and Rescue and RFS arrived on scene to find a Mack tilt tray with cab fully involved," Supt Cotterill said.

Police assisted with traffic management while fire crews doused the flames.

Supt Cotterill said it was not known how the fire started.

"Being a vehicle fire it could have any number of potential causes," he said.

He said initial reports suggested the driver had suffered minor burns, however a NSW Ambulance spokeswoman said paramedics did not attend the fire.