The NZ Transport Agency is asking people to avoid travelling along State Highway 3 near Awakino.
A serious crash about 5 kilometres north of the Awakino Tunnel has closed the road.
The road could be closed for up to four hours.
The NZ Transport Agency says the best way around the crash site for all vehicles is using State Highway 4, however this would add a considerable amount of time to a journey.
It is asking motorists to avoid the area or delay their travel.