Police said they were investigating a crash, understood to involve a single vehicle, on Tiwai Rd, near where it intersects Hall Rd.
The driver of the vehicle died at the scene and the passenger was taken to hospital in a critical condition.
The passenger's condition was later described as moderate and stable.
A police spokeswoman said she could not say if weather played a role in the accident.
''As part of the inquiry by the serious crash unit, this will be looked at.
''The inquiry is still ongoing and no further information is available at this time.''
Yellow lines on the road, left by police investigators showed how the car left the road a few metres after the Hall Rd intersection and ploughed into a deep ditch.
The car had been removed but some minor debris was left yesterday afternoon.
A dairy farm worker, who did not want to be named, said the accident happened shortly after midnight.
''I did not see it, but my wife said she saw the [police] lights at about midnight. I am not sure who called the police, because nobody came to us.''
