The Transport Workers Union (TWU) has called for a review of the trucking of dangerous chemicals in the wake of a catastrophic explosion in south-west Queensland.
A two-kilometre exclusion zone was declared near Charleville after the truck, carting more than 50 tonnes of ammonium nitrate, crashed and rolled about 10:00pm (AEST) on Friday.
It was being transported to South Australia for the mining company, Orica.
Experts from the company were assisting authorities in investigating the accident.
The blast was so powerful it "disintegrated" the truck, destroyed two firefighting vehicles and two bridges, and blew a hole in the Mitchell Highway.
The truck driver, two fire officers, and two passers-by remain in hospital with serious injuries, while three other rescue workers were recovering at home.
TWU spokesman Peter Biagini said there should be restrictions on which trucks could carry which chemicals.
"I think we need to have a good look at this sort of product, and maybe when they are carting these sort of chemicals that the trucks that are carting them should run on natural gas instead of diesel, so if there is an incident like that happened on the weekend you don't have those two products mixing together and causing the explosion," he said.
Queensland Trucking Association CEO Peter Garske said the cause of the crash had to be thoroughly investigated before any discussion could begin on tightening regulations.
"If there's no crash, there's no explosion," he said.
"I'll be looking to cooperating. I've got no doubt my industry and the company concerned will cooperate with all the authorities to see what lessons are to be learned, was it avoidable, was that an issues with the tuck, the driver, the road or indeed some other person on the road as is the case in heavy vehicle crashes."
In a statement, Orica said its team would work alongside emergency services and regulators to understand both the cause of the accident and its aftermath and also provide advice regarding the management of the site and clean up activities.
"The thoughts of all Orica employees in Australia are with the driver of the contractor's vehicle and emergency service workers who responded to the accident and who are now being treated for injuries," the statement said.
"It is not appropriate to speculate on the cause of the accident and subsequent events as these are the subject of the investigations now underway.
"The safe transportation of ammonium nitrate is regulated under the Australian dangerous goods code and in Queensland under the Explosives Act, which is overseen by the Department of Natural Resources and Mines and Inspector of Explosives."Explosion, emergency response to be probed
Fire Assistant Commissioner Tom Dawson said around 20 investigators would return to the scene today, with police and forensic experts already having been granted access to the site on Sunday.
"The rain came in late yesterday afternoon and hampered the work, but the scene is now safe," he said.
"There is a lot more photographic [evidence], more measurements to be taken — a lot more documentation.
"We hope to have that concluded by just after lunch and then we are going to start recovering the vehicles - that's the two fire trucks, and there are two private trucks near the crash scene, as well."
Mr Dawson said authorities would also review the emergency response to the explosion.
The assistant fire commissioner said emergency workers reported problems with telephone and radio coverage at the site in the aftermath of the blast.
"Then you get into sat phones, and if you're not standing in the right place 30 kilometres outside of town your sat phone just won't work," he said.
"You may have to move three or four metres, but you spend half your time trying to find reception and that's when you have time to do it, and you're calm and just looking and you have time to achieve, then you will achieve it.
"But if you're having to think on the spot and move quickly, very challenging."