"The driver managed to get the track or towing unit, but they've got fire engines and God knows what else running around on there."
A Fire and Emergency spokesman said the truck didn't appear to be carrying any dangerous goods.
The fire is between the Gordonton Rd on ramp and the Tahuna Rd offramp.
All northbound lanes between Taupiri and Ohinewai are closed, with traffic being diverted via Huntly. The southbound lanes remain open.
Meanwhile, part of State Highway 3 between Palmerston North and Whanganui was fully closed overnight due to a serious crash.
One person was seriously injured in the crash at Pukepapa Rd at Lake Alice, near Marton, just before 10pm.