New pictures from the crash site of a plane commissioned by the New South Wales Rural Fire Service have been released.

They come as police and investigators begin a probe into how the aircraft came down on Thursday afternoon.

Watch the video above

Three Americans assisting in the firefighting efforts were aboard the plane.

They were captain Ian McBeth, first officer Paul Clyde Hudson and flight engineer Rick DeMorgan Jr.

Their families will be offered an opportunity to visit the crash site, which is northeast of Cooma in regional NSW.

The trio died when their C-130 Hercules plane dropped fire retardant along a ridge and then crashed at Peak View on Thursday afternoon.

Their bodies were recovered a day later.

An investigation into the crash of the firefighting plane is underway. Credit: NSW Police

The victims were captain Ian McBeth, first officer Paul Clyde Hudson and flight engineer Rick DeMorgan Jr. Credit: COULSON AVIATION / PR IMAGE

Australian Transport Safety Bureau investigators on Saturday will make the site safe by securing aviation fuel, the magnesium wheels and any unexploded oxygen bottles before recovering the plane’s voice recorder.

The kilometre-long crash site was “complicated” because it was in an active bushfire area, ATSB chief commissioner Greg Hood said on Friday.

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New South Wales Police are assisting in the investigation and have released pictures of the site.

One shows the wreckage of the plane surrounded by trees charred by bushfires in the region.

Another shows crews wearing HAZMAT suits combing the bushland.

The crash site spans one kilometre in length. Credit: NSW Police

The trio died when their C-130 Hercules plane dropped fire retardant along a ridge and then crashed at Peak View on Thursday afternoon. Credit: Supplied

Representatives of Canadian company Coulson Aviation, which operated the C-130 dubbed Zeus, accompanied a relative in Sydney airport on Saturday.

Coulson has described the three airmen as “fallen heroes” and said the deaths would be “deeply felt by all” in the aviation industry and emergency service sector.

Florida father-of-two DeMorgan, 43, spent 18 years in the US Air Force as a flight engineer on C-130s with extensive combat experience.

His loss was “surreal”, his sister said online.

Investigators set up a base near the site, which is northeast of Cooma. Credit: NSW Police

A police officer and another man look out over the wreckage. Credit: NSW Police

Coulson said McBeth’s love for his wife Bowdie and three children “was evident for anyone who spent time around him”.

Flags will fly at half-mast on Saturday in Montana, where the highly qualified 44-year-old pilot flew with the National Guard.

Hudson, a 42-year-old from the outskirts of Phoenix, spent 20 years as a US Marine, flying C-130s and receiving many decorations as he reached the rank of lieutenant-colonel. He is survived by his wife Noreen.

The trio died when their C-130 Hercules plane dropped fire retardant along a ridge and then crashed at Peak View. Credit: NSW Police

Investigators in HAZMAT suits probe the area. Credit: NSW Police

“Arizona is heartbroken by this news,” Arizona Governor Doug Ducey said.

“First Officer Paul Hudson was a hero who dedicated his life to service, first as a Marine, then as a firefighter. And when help was needed to fight wildfires in Australia, he didn’t hesitate.”

- with AAP