The employer of a pilot missing after a helicopter crash in an isolated area of North Canterbury says there is nothing at this stage to indicate the cause.
Michael Graeme Mehrtens was the sole occupant of the helicopter, which is believed to have crashed into Lake Sumner on Monday.
The 35-year-old failed to return after spraying gorse for the Department of Conservation near the lake.
Police say a small amount of debris has been recovered on Tuesday and an oil slick was spotted offshore from Breaksea Bay.
Rob Kittow, of Rangiora-based Way to Go Heliservices, says he is deeply shocked by the crash and the company will investigate its cause.