Defense Force communications director, Commander Phil Bradshaw, said in a statement there would be no official comment until the force had established what happened.
Police and ambulance services said they found three dead at the scene on farmland about 25 miles (40 kilometers) northeast of Wellington after responding to an emergency call about 6:45 a.m. local time (1845 GMT Saturday).
A fourth person had serious injuries and was transported by ambulance to hospital.
Local resident Kathy McLauchlan, who could see the crash site from her window, said weather conditions at the time of the crash were "extremely misty. Since the mist has lifted, we can see it."
Military and civilian rescue helicopters were at the crash quite high on the hills, she said.
Written by Associated Press