Five people have been flown to hospital after a helicopter crash, east of Waiouru.

One is in a critical condition, and two others have serious injuries.

The chopper went down during a commercial surveying operation this morning.

Search and Rescue co-ordinator Dave Wilson says air ambulances were called for all five on board.

"All of the patients were taken back to Hastings. We understand they were all admitted to hospital for at least some period of time."

Accident investigators will arrive at the scene early tomorrow.