Emergency services are working on a truck fire on Transmission Gully motorway, north of Wellington, and all but one lane is closed.
The fire was in the southbound lane of State Highway 1, between Paekakariki and Pauatahanui.
Motorists are being asked to avoid the area, and to take another route.
Police said they were called about the truck fire about 8.30am.
Traffic management was in place at the scene while the fire was being put out.
Waka Kotahi said the road was closed to all southbound traffic, but one lane remained open for northbound traffic.
It recommended using State Highway 59 instead.