The road was partly blocked, the police spokeswoman said.
Police were called to the scene about 9.50am.
Jean Wicks lives nearby and said she could see flashing lights after the crash, but emergency services vehicles were starting to leave.
The crash had occurred on "the top of the hill", she said.
Yesterday afternoon, a father and son died in a crash involving a tanker near Marsden Point in Northland.
An unmarked police car heading to the smash has also collided with another vehicle, injuring two police officers and the driver of the other car.
The crash, which happened about 12.10pm, blocked State Highway 1 about 500m north of the Mangapai intersection until about 1.45pm.
Senior Sergeant Ian Row, of Northland road policing, said initial investigations showed a 31-year-old man was driving towards Refining NZ when he lost control on a straight stretch of road in heavy rain.
His 13-year-old son was sitting in the front passenger's seat.
"The car spun out of control and hit the tanker backwards. The tanker driver had slowed down to almost zero because he was only a short distance away from turning right for a local delivery," Mr Row said.
He said the car, which police believe was a Honda Civic, spun off to the side of the road from the impact.
Both occupants were locals and died at the scene.
The tanker driver was unhurt.
A woman has died overnight from injuries she received after crashing her car into a tree in North Waikato yesterday.
The 34-year-old woman was driving on Tauhei Rd, about 15km north of Morrinsville, when she crashed just before 2pm, police said in a statement.
Her husband received minor injuries, but the woman had to be freed from the vehicle by emergency services.
She was flown to Waikato Hospital but died about midnight, police said.
In Christchurch, a motorcyclist was killed and another person injured after the motorcycle collided with a car.
That incident happened on Queen Elizabeth II Drive shortly after 9.15pm.
St John confirmed one person had died. The driver and sole occupant of the car suffered minor injuries.
