I've talked to a 2Degrees spokeswoman and she says more information is forthcoming but they can't confirm anything yet.
More information about the accident on NZ Herald.
Auckland's Westpac rescue helicopter has been sent to the last known position of the aircraft and identified an oil slick and wreckage about 11 nautical miles (20km) north west of the entrance to Kawhia harbour, near Gannet Island.The aircraft was a twin-engine Beechcraft Baron.
RCCNZ Search and Rescue Mission Controller John Dickson said the aircraft radioed to report engine failure shortly before radar contact was lost.
"A helicopter from Phillips Search and Rescue in Hamilton is searching the area, along a fixed-wing Coastguard area, and a Raglan Coastguard vessel is also on scene and is picking up debris," he said. 'Unfortunately there has been no sign found of the people onboard."
The water in the area is about 60m deep.