A section of State Highway 1 on the Waikato Expressway is now closed after a number of crashes on the fog-affected road.
Heavy fog has resulted in "multiple crashes" on the expressway, initially closing both southbound lanes early this morning.
Now police have said the highway near Hampton Downs is closed to traffic in both directions while the road is cleared.
Emergency services earlier responded to reports of at least two crashes - one involving a truck.