The cockpit voice recorder from the C130 air tanker that crashed in the Snowy Monaro region on Thursday has been recovered from the charred site.
The bodies of three men involved in the air tanker crash were recovered on Friday and taken to Sydney under police escort.
Investigations into what caused the crash at Peak View, about 50 kilometres north-east of Cooma, are ongoing.
On Saturday morning, the site was handed over from NSW Police to the Australian Transport Safety Bureau. In an initial sweep, bureau investigators found the cockpit recorder in the wreckage, near the tail of the aircraft which was about all that remained.
The recorder has been taken to a technical facility in Canberra.
Australian Transport Safety Bureau chief commissioner Greg Hood said the voice recorder "could be very useful for us, and it might not be very useful for us".
"It really depends on what was said," Mr Hood said.
"[It] generally records the last two hours of the flight. It will record the pilot, the co-pilot and the flight engineer's discussion in the cockpit. It will also record any alarms or warnings that might have been issued in the cockpit as well.
"Without knowing exactly what happened, we don't know how useful that piece of equipment is but we remain hopeful that it will assist us in the investigation."
Mr Hood said he would know on Sunday, after the data had been downloaded, whether it would be useful to the investigation.
In the meantime, the bureau is taking statements from Rural Fire Service firefighters who witnessed the crash.
A 3D mapping drone will be taken to the site on Sunday, which wasn't possible on Saturday as the area is still an active fire zone and water bombing helicopters were active throughout the day.
Mr Hood described mapping the crash location as a "painstakingly meticulous" task.
"It's quite a wide debris field. We're required to map all of those pieces of debris," he said.
The bodies of 44-year-old Ian McBeth, first officer Paul Hudson, 42, and flight engineer Rick DeMorgan Jr, 43, were recovered on Friday night. They were taken to Canberra and then on to Sydney, travelling under police escort.
Montana father-of-three, captain Mr McBeth, was a long-time firefighter who served in the military and the Wyoming and Montana air national guards.
First officer Paul Hudson, from Arizona, spend 20 years in the US Marine Corps where he was a C-130 pilot among other roles.
Father-of-two, Florida flight engineer Rick DeMorgan Jr, served in the US Air Force and spent 18 years as a flight engineer on the C-130.
The three men were helping to fight fires in the region.
Coulson Aviation, the Canadian aerial firefighting company operating the plane, said the men were fallen heroes.
Relatives of the men were due to arrive in Australia over the weekend, and would be offered the opportunity to visit the crash site.
NSW Rural Fire Service Commissioner Shane Fitzsimmons said the state would "forever be indebted" to the sacrifice the three men made.
"It's a confronting and sobering reminder of the enormity of the risk and challenge associated with this fire season and all the firefighting effort that goes along with it," Mr Fitzsimmons said.