Prosecutors in China have formally arrested four employees of Rio Tinto mining company on suspicion of violating commercial secrets and taking bribes.
Rio Tinto executive Stern Hu and three Chinese employees, Liu Caikui, Ge Minqiang, and Wang Yong, were originally detained on 5 July.
The official Xinhua news agency says they are suspected of "using improper means to obtain commercial secrets about China's steel businesses'.
They were accused of bribing employees of Chinese steel companies during the latest round of iron ore price negotiations.
Rio Tinto had no immediate response to the report, but has previously said that the four detained employees did nothing improper.
The State Secrets Bureau website said on Sunday that Chinese steelmakers had lost 700 billion yuan ($A122 billion, $US102 billion) through overpaying for imported iron ore for six years.