The search for missing Wanaka helicopter pilot Matthew Timothy Wallis has been suspended for the night.

Police confirmed earlier today the 39-year-old Wallis was the only person on board a helicopter which went down at Lake Wanaka about lunchtime yesterday.

The Police National Dive Squad bega​n a search of the lake this afternoon.

The search will resume at first light tomorrow.

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Detective Sergeant Derek Shaw said the area was under a severe weather watch yesterday and police no longer expect to find Wallis alive.

"We have now transited into a recovery phase and we do not believe that the pilot is still alive," he said.

Matthew Timothy Wallis, the only person onboard. Photo / Supplied
Matthew Timothy Wallis, the only person onboard. Photo / Supplied

Shaw made the comments in a media briefing this afternoon.

Reports suggest Wallis crashed his R44 Robinson helicopter near Stevensons Island in Lake Wanaka.

Shaw said the national dive squad arrived this morning and are focusing their search near an oil streak which was located yesterday.

"They are going to investigate the oil slick that has stopped coming up from the lake, but the marker indicated where that was.

"They've arrived in Wanaka and already deployed and they should have an indication of what they'll face by this evening.

He said Alpine Helicopters initially started the search after reporting that one of their helicopters was missing around 1pm yesterday.

They dropped a marker in the Stevensons Arm area after finding the oil streak and debris in the water.

Wreckage of the crash was found on the shoreline of nearby Stevensons Island, as well as an oil slick found in the water 1km north.

The Maritime Rescue Coordination Centre, police and Coastguard are all involved in the search that was suspended last night until this morning.

Statement from Alpine Helicopter:
At 12.54pm on Saturday, July 21 a helicopter left its base with one person onboard on a private flight from Wanaka Airport to Mount Aspiring National Park. The flight was expected to take approximately 15 minutes. At 1.08pm the helicopter was unable to be reached by radio. Its last satellite position report was 1.03pm. At 1.16pm the aircraft was deemed overdue and at 1.19pm two aircraft were sent to search for the missing helicopter and pilot. Items specific to that aircraft were located in Stevenson's Arm Lake Wanaka. The aircraft and pilot, Matthew Wallis, are now considered missing. We would ask for respect for an ongoing search operation and will update in due course.

The location of the crash. Graphic / NZ Herald
The location of the crash. Graphic / NZ Herald

Six helicopters have been involved in the search, including the three choppers from the company owning the missing craft.

A police spokeswoman said then that it had received reports of a downed helicopter, but said Maritime New Zealand's Rescue Coordination Centre was leading the operation.

Metservice meteorologist Ravi Kandula said yesterday had been a "cloudy, gloomy day with reduced visibility" since about midday in Wanaka.

There had been occasional steady rain, and cloud had dropped to about 1000-1200 feet.

While there had been some gusts late morning, the wind had not been "spectacular" for most of the day.