The national transport safety bureau will investigate how a freight train carrying more than 800,000 litres of sulfuric acid derailed in northwest Queensland.
Queensland Transport Minister Stirling Hinchliffe made the announcement late on Tuesday, three days after the 26-carriage train overturned at the Quarrells site, 20km east of Julia Creek.
"By engaging the Australian Transport Safety Bureau in these early stages we can ensure the incident is thoroughly investigated and that we receive the best advice in a timely manner," he said in a statement.
A preliminary report will be released in February and recommendations made before September next year.
Police say the train was carrying 819,000 litres of the highly corrosive acid, of which 31,500 litres leaked from one carriage.
Heavy rain and muddy ground have hampered efforts to reach the train, roughly 100m from the nearest road.
Police began working at the site on Tuesday afternoon.
Queensland Rail said staff had not been able to access the site as a police exclusion zone of two kilometres was in place and was not expected to be lifted until at least Thursday.
A spokeswoman said it was too early to say how long the clean up would take, but police have said it could take weeks.
The Flinders Highway between Julia Creek and Richmond, as well as train lines in the area, were still closed on Tuesday evening.
