Chinese authorities have extended their investigation into a Rio Tinto executive arrested for alleged spying, but the full case against him remains unknown, an Australian official said on Friday.

Stern Hu, Rio Tinto's lead negotiator in iron ore price talks, was detained in Shanghai in July on allegations of spying and bribery. Chinese officials later indicated he would face charges of industrial espionage.

"I can confirm that the investigation into Stern Hu has been extended," a spokeswoman for the Australian Department of Foreign Affairs told AFP.

"Mr Hu has been formally arrested on suspicion of violating commercial secrets and taking bribes. Full details of the actual charges are not likely to be known until he is brought to trial."

The arrest of Hu, along with three Rio Tinto colleagues, prompted the Anglo-Australian mining giant to suspend iron ore negotiations with China and raised tensions between Canberra and key trading partner Beijing.

Rio, which has said iron ore sales to China have been "maintained at a high level" despite the arrests, has denied accusations that Hu bribed steel mill officials during failed talks aimed at setting annual iron ore prices.

His arrest came just weeks after Rio snubbed a $19.5-billion injection from China's Chinalco in favour of a major rights issue and iron ore joint venture with fierce rival BHP Billiton.

AFP

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