The search for a pilot missing after his helicopter crashed into an isolated lake in north Canterbury this afternoon will continue tomorrow.
It is believed the helicopter had been contracted by the Department of Conservation (DOC) to spray for gorse when it went down at the northern end of Lake Sumner.
Police were contacted by DOC at about 2.50pm when the helicopter failed to return to base.
A police spokesman said no wreckage, nor the pilot, had been found yet.
The area is part of the Lake Sumner Conservation Park.
The Westpac Rescue helicopter has this evening been searching in the Lake Sumner area for signs of the helicopter.
Police said the search will resume at first light tomorrow at Lake Sumner in North Canterbury.
Garden City Helicopters pilot Neil Scott said access was difficult in the "inhospitable'' mountainous terrain.
A Fire Service spokesman said the search and rescue operation would be co-ordinated from a nearby farm.
A spokeswoman for the Civil Aviation Authority said investigators were still receiving information about the crash.
Decisions about sending investigators to the scene would be made after emergency services had reached the wreckage.
She said an investigation would depend on the seriousness of the crash.
It has been reported that the helicopter was a Robinson 22.
There have been numerous investigations into past crashes of Robinson 22s, including one last year by the Transport Accident Investigation Commission (TAIC).
An inquiry was launched after two pilots were killed in a helicopter crash in Mount Aspiring National Park in April 2011.
They were on a training flight when their Robinson 22 helicopter went down on the Arawhata Saddle at the head of the Matukituki River, about 50km northwest of Wanaka.
In October 2010, a learner pilot and his instructor were killed when the Robinson 22 chopper they were in crashed in Bluff Harbour.
Student pilot Allan Munro, 67, was believed to have been practising a simulated engine problem exercise when the chopper crashed killing him and instructor Jason Wright, 29.
Investigation results released this year said the crash was likely caused by student pilot error.
The pilot of another Robinson 22 was killed in April last year when the chopper crashed into the Mistake Basin area of the Rolleston Range.
Adrian Mayberry, 59, died at the scene.
His son-in-law, Nev Sarginson, was pulled from the wreckage alive.