Update 9pm: 2Degrees has confirmed the plane involved in the crash near Kawhia is owned by Eric Hertz, the company chief exec. Hertz and his wife were on board the plane.
"Although we have limited information, we understand that Eric and his wife Kathy were on board and that they are unlikely to have survived," says a 2degrees statement.
"Our focus now is to support Eric and Kathy's daughter and provide assistance to their family."
Update 7:50pm: An NZ Police spokesperson confirms the plane is registered in the US. Police know the names of the individuals on board, but are not sharing this information at this time. The search operation has ceased for the night and is scheduled to resume tomorrow morning
(Heric Hertz at 2Degrees' millionth customer milestone)
The twin engine plane, which was traveling from Ardmore to Timaru, is owned by the American Hertz.
The Coastguard is at the scene and a Westpac Rescue Helicopter has found wreckage 11km northwest of the Kawhia harbour, according to Maritime New Zealand.
More as this story develops.