Investigators are working in challenging conditions at Mount Disappointment, north of Melbourne, to unravel what led to "one of the worst" aviation tragedies in Victorian history.
The Australian Transport Safety Bureau's chief commissioner Angus Mitchell said air safety investigations were "very complex" but hinted at some of the factors in Thursday's helicopter crash which killed all five people on board.
"We will look at what we can gather from the site, and as you can imagine, that is very challenging in a situation like this where we've had a collision with terrain and potentially a fire," he said.
He said getting access to the "heavily wooded" site had initially been the main focus of authorities.
Mr Mitchell said once in, his team had begun trying to get a picture of the flight path the helicopter was on in its final moments and "particularly where it may have impacted any of the trees and what story that can tell us".
Late on Thursday, more than 10 hours after the helicopter that had been part of a convoy of two disappeared, police confirmed that four passengers and a pilot had died.
Here is what we know about the tragic crash.
Who was on the flight?
Those killed in Thursday's crash were four men and a woman.
The woman was from Inverloch, aged 50, and the men were a 32-year-old from Cheltenham, a 73-year-old from Albert Park, as well as a 59-year-old man and 53-year-old man from New South Wales.
Meat industry leader Paul Troja has been identified as the 73-year-old victim of the crash.
The chairman of Radford Meats at Warragul is being remembered for his long and accomplished career within the industry.
The family of the helicopter's pilot, 32-year-old Cheltenham man Dean Neal, said they were "shocked and distressed" at the loss of their son.
They said their "broken hearts go to the families and friends of those who were flying with him" and said they understood their "unspeakable loss".
Blockchain company AXIchain confirmed its CEO Linda Woodford and finance consultant Ian Perry were also killed in the crash.
AXIchain said the pair was travelling to regional Victoria to visit clients.
"Linda was a driven visionary and an eternal optimist and will be deeply missed by all that knew her," a spokesperson for the company said.
"Ian was a respected member of the agricultural industry and a committed family man and will be sorely missed by all that knew him."
Helicopter flight operator Microflite confirmed yesterday that the helicopter that crashed was one of two in a charter convoy being run by the company and the deaths included one of its "highly respected" pilots.
Each of the two helicopters travelling in the convoy had a pilot employed by Microflite and four passengers on board.
The second helicopter landed safely soon after the first went missing.
Yesterday the company publicly expressed its "deep condolences" and it has put a pause on its services until at least next Tuesday, April 5.
Where were they going?
The two helicopters first took off from Moorabbin Airport in Melbourne's south-east, before picking up passengers from Batman Park in the city at about 7am.
According to police, the two helicopters were chartered for a business trip and were both headed to Ulupna Island in Victoria's far north for a meeting.
Police said trouble struck just after 9am as the two aircraft made their way over Mount Disappointment, a peak about 60 kilometres north of Melbourne that sits at the southern end of the Great Dividing Range.
Acting Inspector Josh Langelaan said the helicopter that crashed disappeared in an area of low cloud.
"There was low cloud this morning, one helicopter came through the cloud, found that the other one was missing and police were notified," he said.
Victoria Police's Air Wing located the site of the wreckage, near Blair's Hut, just before midday but, due to the difficult nature of the terrain, it took until almost 4pm for emergency services to reach the site on foot.
Heavy machinery such as excavators and bulldozers were used to help reach the wreckage in the bushland.
The worst was feared from early on, but it wasn't until Thursday night that police were able to confirm publicly that all five people on board the helicopter had died.
When will we find out what went wrong?
Police guarded the site overnight before handing the investigation to specialists from the ATSB.
The ATSB's Mr Mitchell said his organisation was investigating eight separate fatal aviation accidents that had taken place across six Australian states over the past three months.
"Yesterday's represents one of the worst in Victorian history, certainly since the 2017 accident at Essendon Airport," he said.
In February 2017, five people were killed after a plane plunged into a shopping centre near the airport.
He said to better understand the Mount Disappointment crash, investigators would reconstruct a three-dimensional version of the scene.
"We'll gather anything that we can, whether it be recorders, whether it be anything that the passengers may have had on them at the time," Mr Mitchell said.
He said software and drones would be used to build a picture of the crash site, and other factors would be considered in a process expected to take "many months".
"That's to go through maintenance records, to go through qualifications, to look at things like the weather that was forecast for yesterday plus what was the weather experienced on the day," he said.
"We'll also look at loading of the aircraft and its tasking.
"Our main goal here is not only to work out what occurred and what brought the helicopter down, but equally, what are some of the lessons that may be learnt so we can prevent instances like this occurring into the future."
He said at this stage it was believed there was no distress call from the helicopter that crashed, and he said generally helicopters of that kind were not required to carry recording devices.
Mr Mitchell said any urgent safety issues that arose would be passed on immediately, but a preliminary report into what caused the crash would take between six to eight weeks to be released.
Acting Inspector Langelaan said the tragic events of the morning of March 31 had affected emergency services personnel, some of whom were winched in to help with the on-foot search for the wreckage.
"It's been a trying day for the emergency services and I just feel for the family and friends [of the deceased]," he said.
