The wreckage belonged to the helicopter carrying retired businessman turned landscape photographer Richard Green, his graphic artist wife, Carolyn Green and their travelling companion, renowned documentary maker John Davis.

A search and rescue helicopter spotted the wreckage on Monday evening and a paramedic was winched down to the site in search of survivors.

The bodies of all three were found among the wreckage, the Australian Maritime Safety Authority (AMSA) confirmed.

The crash site is in mountainous terrain, covered with dense vegetation. Weather conditions in the area were severe on Saturday, with localised thunderstorms and rain, AMSA said.

The search got under way on Monday after authorities were notified that the privately owned EC135 helicopter which left Breeza, south of Tamworth, on Saturday evening bound for Mona Vale had not arrived.

A friend of Mr Davis, Dr Brian Spies, said the purpose of the helicopter flight was to film coal mines in the area for a documentary they were working on.

Mr Spies said Mr Davis - a veteran filmmaker - and fellow environmentalists Mr and Mrs Green, were planning to use the footage to expose the environmental damage wrought by the coal mines.

"It's a terrible loss for their friends, the environmental movement and the documentary community," Dr Spies said.

The Greens and Mr Davis attended the Harvest Festival at Breeza against Shenhua's coal mine but left after a few hours. Their flight to Sydney's northern beaches should have taken two hours and no mayday call or emergency beacon signal had been detected.

Authorities were notified on Monday morning that the twin engine helicopter had gone missing. By Monday night the Australian Maritime Safety Authority had narrowed the search area down to a 345 square kilometre area south of Cessnock in the Hunter Valley.

"There has been no mayday call or emergency distress beacon signal associated with the helicopter," the authority said.

Mr Davis and his wife Felicity Davis were both Greens candidates for Davidson and Pittwater respectively in recent elections.

Mr Green, on his photography website, said he and his wife use the helicopter as a "flying camper van" to "find, access and photographically record some of Australia's most remote, wild and beautiful environments".

"After early retirement from a successful business career in England, I decided to take up the challenge of learning to fly a helicopter," he states.

"I subsequently purchased my own, and emigrated to Australia where I met Carolyn. For over 20 years we have made regular helicopter trips together to distant and otherwise inaccessible outback locations - our objective being to find and photographically record some of the continent's most remote, wild and beautiful environments.

"The helicopter has been specially modified to act as a self-sufficient camp base."

Investigators have been told that the Greens are known to stop off at places during their helicopter trips to go bushwalking or exploring for days at a time. The helicopter also has some modifications to make it fly for longer.

Fairfax Media understands a mobile phone signal was picked up south of Sydney since Saturday.

Mr Green's website also appears to have been updated on Monday.

In the "news" section, there is a post dated 9.11.2015 in which Richard writes about just returning from a month-long helicopter trip to the Simpson Desert, Kimberley, Pilbara, Nullarbor Plain, Adelaide and Melbourne.

Andrew Pursehouse, who owns the Breeza property where the Greens' helicopter landed and took off from, said Mr Davis called ahead on Saturday morning to ask for the co-ordinates of the property.

Mr Pursehouse said they landed near a shed on Breeza Station just after 11am, stayed for some speeches and left about 3.30pm.

Before they left, the Greens asked a local man for directions to the Whitehaven mine at Werris Creek, about 50 kilometres from Breeza.

"There are some environment issues and they wanted to have a look at that, obviously," he said.

Mr Pursehouse said police rang early on Monday morning to ask for the details of the pilot. They later told him that Mr Davis' family had reported those on board missing.

AMSA and the Westpac Rescue Helicopter had originally coordinated a search for the chopper throughout the Hunter Valley region and Sydney.

A search and rescue plane was scouring the northern boundaries of the search areas along the helicopter's assumed flight path on Monday afternoon.

A rescue helicopter was searching the southern portion of the search area but that was later scaled back to the area south of Cessnock on Monday night.

"AMSA extends its condolences to the families and friends of those on board the helicopter and thanks all those involved in the search," an AMSA statement read.

- with the Northern Daily Leader