SYDNEY, Jan 11 (Reuters) - A Chinese investigation into a detained Australian Rio Tinto Ltd mining executive has been sent to prosecutors, Australian media said on Monday.
Four Rio staff, including Australian citizen Stern Hu, have been in Chinese custody since July over accusations of illegally obtaining commercial secrets.
The case, which has caused tensions between Australia and China, has placed a cloud over already contentious iron ore price negotiations between China and miners Rio, its fellow Australian miner BHP Billiton and Brazil's Vale.
China is Australia's biggest trade partner, with trade worth $53 billion last year. (Reporting by Michael Perry; Editing by Jeremy Laurence)