UPDATE:
One person has been extracted from the car and taken to Rotorua Hospital by ambulance.
A police spokeswoman said the cause had not been determined but it was a timely reminder to be wary of frosts making roads slippery as we move into the colder months.
EARLIER:
State Highway 33 near Okere Falls is still down to one lane with police, fire and ambulance at the scene of a serious crash.