A man is in a critical condition in Waikato Hospital and a mother and her two children have also been injured after a vehicle rolled near Taupo.
The four people, from Taupo, were injured when their 4WD rolled at noon on Saturday, on the East Taupo Arterial bypass just north of the Centennial Dr interchange.
A 25-year-old male driver, a 25-year-old woman and her two children - aged 6 and 1 - were flown to Waikato Hospital by the three rescue helicopters from Rotorua, Taupo and Hamilton.
Taupo police Senior Sergeant Fane Troy said the cause of the crash was being investigated by police.
The two children and their mother, who was cut free from the passenger seat by the Taupo Fire Service, were in a stable condition at Waikato Hospital yesterday.
However, the 25-year-old driver is still being treated in the intensive care unit and is in a critical condition.
Mr Troy said all the passengers were wearing seatbelts and a children's car seat limited the injuries.
The road and weather conditions were fine at the time of the crash and the speed limit in the area was 100km/h.
The road was closed for about four hours.