Aviation safety experts are expected to begin combing through the wreckage of a helicopter that crashed in mountainous Victorian terrain, killing five people.

Four passengers and a pilot died at the scene after the aircraft crashed at Mount Disappointment, north of Melbourne, on Thursday morning.

The five people on board as 50-year-old woman from Inverloch, a 32-year-old man from Cheltenham and a 73-year-old from Albert Park (all in Victoria), and men aged 59 and 70 from NSW.

Their remains were found after ground crews battled steep terrain and dense forest to reach the wreckage near Blairs Hut about 3.45pm, after it was earlier spotted by the police air wing.

“The helicopter’s been destroyed and unfortunately there were no survivors,” Acting Inspector Josh Langelaan said on Thursday night.

It is believed to be Victoria’s deadliest aviation disaster since February 2017, when five people were killed after a charter plane crashed into Melbourne’s Essendon DFO shopping centre.

At the time, Premier Daniel Andrews said that was the state’s worst civil aviation accident for 30 years.

The helicopter was one of two that departed Batman Park in central Melbourne on Thursday morning, flying in convoy over Mount Disappointment on their way to Ulupna near the Victorian/NSW border.

The passengers were travelling as part of a business trip, police said.

SES crew and Victoria Police at a road block near the command post at Blairs Hut. Photo: AAP

Mr Langelaan said there was low cloud over Mount Disappointment when one of the helicopters went missing. The other raised the alarm, before landing safely.

The cause of the crash remains unknown, with the Australian Transport Safety Bureau to take over the investigation on Friday.

It will send a team to the site from its Canberra and Melbourne offices with expertise in helicopter operations and maintenance, as well as aerospace engineering.

They will inspect the wreckage and site surrounds before sending any relevant parts to Canberra for further examination.

The ATSB will also analyse recorded data and carry out interviews with those who have knowledge of the flight.

A preliminary report from the watchdog is expected in six-eight weeks.

Bulldozers and an excavator have been called in to clear a path to the crash site through the rugged terrain. The ATSB is expected to remain on site for several days.

-AAP