Police are investigating whether the driver of a mini-van that collided with a milk tanker had fallen asleep at the wheel.
The van driver, Andre Vogel, 36, and student Gabriel Runge, 16, were killed when the van collided head on with a milk tanker south of Rotorua on Friday.
Police said the van was travelling on the wrong side of the road when the crash happened on State Highway 5 near Reporoa.
They said their investigation was not complete but they were looking into the possibility the driver may have fallen asleep at the wheel.
Their findings will be passed on to the coroner when the investigation is complete.
The other five students in the group, from the Noosa Pengari Steiner school in Queensland, Australia, returned home at the weekend. They had been in the country country on a school trip.