China's security watchdog has accused Rio Tinto of spying on Chinese steel companies over an extended period of time.
The ABC reports the National Administration for the Protection of State Secrets claims that spying has cost China 700 billion yuan ($A122 billion) in higher payments for Australian iron ore over the past six years.
It says that Rio Tinto's spying included "winning over and buying off, prying out intelligence, routing one by one and gaining things by deceit".
The security agency also says that a large amount of intelligence and data on Chinese steel companies was found on the seized computers of Rio Tinto personnel.
Rio Tinto's head of iron ore sales in China, Stern Hu, and three Chinese co-workers were detained on 5 July on suspicion of spying and selling state secrets. They are still being held.
State media in China say they are suspected of paying bribes for information on China's negotiating stance on the price of iron ore.
Chinese news reports say executives of at least five major Chinese mills are being questioned.
Rio Tinto is the world's second-largest iron ore producer. It has refused to comment on the report.