A team of aviation experts will spend at least three days combing through wreckage to determine the cause of a Victorian helicopter crash.
The aircraft came down at Mt Disappointment, north of Melbourne, on Thursday morning, killing a pilot and four passengers.
Meat industry boss Paul Troja, 73, has been identified as one of the victims.
The Albert Park man's fifth grandchild was born a day earlier, his son Luke Toja told Nine News, revealing his father vowed this trip would be his last before retiring.
Mr Troja, the chairman of Warragul-based meat processing company Radfords, has been remembered as a passionate and accomplished leader.
A 50-year-old Inverloch woman and two NSW men, aged 59 and 70, were also on board the helicopter, flown by a 32-year-old Cheltenham man.
Australian Transport Safety Bureau Chief Commissioner Angus Mitchell said crews from Canberra and Melbourne will take at least three days to analyse the helicopter crash site.
"What we do know is it was in company with another helicopter from the same operator and that they lost visual contact," Mr Mitchell said.
Drone analysis of the helicopter's flight path, along with assessment of flight control records and weather conditions, will be part of the investigation.
Mr Mitchell said the helicopter operator Microflite had a very strong safety record.
The company has suspended all services until at least Tuesday.
"The Microflite family have been deeply shocked and devastated by this tragic incident," the company said in a statement, which also acknowledged the loss of a highly respected pilot.
The crash is 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.
That crash was the state's worst civil aviation accident for 30 years.
The helicopter that crashed was one of two flying business trip passengers in convoy from Batman Park in central Melbourne to Ulupna, near the Victoria/NSW border.
The other raised the alarm before landing safely at Moorabbin.
There was low cloud over Mt Disappointment the morning of the crash, police said.
Victoria Police Chief Commissioner Shane Patton said the crash investigation was complex because of the rugged terrain and wreckage strewn across the area.
It took investigators four hours to reach the scene after the chopper was first located by air wing.
Bulldozers and graders are expected to finish creating an access road to the site by Friday afternoon.
"It's difficult terrain. It is not friendly for people just to wander into," Mr Patton told reporters in Melbourne.
"We don't want to leave any stone unturned."
Victorian Police Minister Lisa Neville thanked emergency services for their efforts on the ground and passed on her condolences to the victim's families.
"It's been a terrible tragedy," she said.
"I know that there'll be many families, friends and colleagues grieving and my thoughts are with them."
The ATSB's preliminary report is expected to take six to eight weeks.
