The vehicle was lost in the Hobsonville Road area, close to the new Northwestern Motorway interchange. The spokesman said shortly afterwards, police officers found the vehicle had crashed.
The spokesman said a police inspector was at the scene and would remain there until early in the morning.
Traffic would be diverted.
A spokesman for St John Ambulance said their staff were called to help at 1.05am. The person who called said a car had rolled and crashed, leaving five poeple injured and trapping in the car.
The people trapped were forced to wait in the wreckage for more than 20 minutes as fire crews fought furiously to free them.
The St John spokeswoman said there was one dead person, one with critical injuries, two with serious injuries and one person with moderate injuries.
She said the three people with the most serious injuries were taken to Aucklnad City Hospital. The other person was taken to North Shore Hospital.