A water tanker that crashed in NSW had dropped fire retardant along a ridge before it hit the ground and exploded, the transport safety bureau says.

The bodies of three US firefighters who died when their water-bombing aircraft crashed in southern NSW have been recovered with authorities now focused on determining what caused the fatal incident.
The families of captain Ian McBeth, first officer Paul Clyde Hudson and flight engineer Rick DeMorgan Jr are expected to arrive in Sydney this weekend along with the owners of the C-130 Hercules which was operated by Canadian firm Coulson Aviation.
The water tanker crashed on Thursday afternoon just after it had dropped fire retardant along a ridge at Peak View northeast of Cooma, Australian Transport Safety Bureau Chief Commissioner Greg Hood said on Friday.
The NSW RFS mourns the loss of the three crewmembers, killed in yesterday’s Large Air Tanker crash. Our thoughts are with their families, fellow crewmembers and the broader emergency services family that knew and worked with them. #nswrfs#nswfirespic.twitter.com/u894hOC9fS
NSW RFS (@NSWRFS) January 24, 2020
The safety bureau boss revealed the kilometre-long crash site was “complicated” because it was in an active bushfire area.
ATSB investigators are now on-site and on Saturday afternoon, released confronting photos of the crash site.
Before beginning work, investigators were required to make the site safe by securing aviation fuel, the magnesium wheels and unexploded oxygen bottles.
 It’s expected they will attempt to locate the plane’s voice recorder and take it back to Canberra “to see what the exchanges may have been in the cockpit during those final moments”, Mr Hood told reporters.
“We have upwards of 500 firefighting aircraft active across the country from about 150 companies and several different countries,” Mr Hood said.
“So if there are lessons to be learned from this particular accident it’s really important that Australia and the world learn them.”
Members of Coulson Aviation arrived in Sydney on Saturday afternoon, it’s believed family members of the three Americans have also touched down.  
The death toll from NSW’s unprecedented bushfire season climbed to 25 on Friday evening after the body of a 59-year-old man was found in a home on the state’s South Coast.