Rescuers have found wreckage at Lake Wanaka that may be from a helicopter reported missing.
A helicopter company had earlier reported that one of its Robinson helicopters was overdue and had disappeared from its tracking systems.
Three helicopters from the same company retraced the flight path of the missing Robinson and found an oil slick one kilometre north of Stevenson Island and wreckage on the island's shoreline.
The Rescue Coordination Centre said it was working with police, Coastguard NZ, a Land Search and Rescue team and two additional helicopters to expand the search.
Searchers will scour the Lake Wanaka area, where the oil slick was seen.
Another team is to land on Stevenson Island.
The Transport Accident Investigation Commission has opened an inquiry into the crash.
Two accident investigators are due to arrive at the crash site tomorrow.