A person has died after the van they were driving near Queenstown ploughed into the back of a truck carrying a house.
The crash took place about 8.45pm on the Gibbston Valley Highway (State Highway 6) just west of the Kawarau Bridge.
St John said two ambulances went to the crash and treated one patient, who died.
A journalist at the scene said it appeared the van had been trying to overtake the truck on a stretch of 100km/h road before careening into the back of it and spinning into a ditch.
The entire front of the late model white van can be seen crumpled in on itself in photos from the scene.
The crash took place on an open stretch of road that was slightly veering left and uphill.
Glass is also strewn 100m along the highway but little damage was done to the truck, the journalist said.
He expected the road to be closed for hours.
The serious crash unit and the commercial vehicle safety team were attending, police said.
Traffic diversions were in place and motorists were advised to avoid the area if possible.