Four people are believed to be hurt - with one critically injured - following a serious crash near Warkworth, north of Auckland.
The crash involving two vehicles occurred about 11.30am on State Highway 1 in Dome Forest.
Emergency services were at the scene and closed the road.
Motorists were warned to expect delays and diversions on SH1 at Kaipara Flats Road to the south - and at Wayby Valley Road to the north.
Police advised motorists to avoid the area and for those travelling between Wellsford and Auckland to take the alternative State Highway 16 route.