China's probe into alleged bribery and spying by employees working for Rio Tinto has now been widened to include executives at five steel groups based in the country.Baosteel, Anshan Iron & Steel, Laigang and Jigang are the latest steel producers to be investigated into possible rigging of iron ore prices, the China Daily said. Last week, the Chinese detained an executive at Shougang, another major steel producer.Baosteel, Shougang and Angang are currently engaged in talks to decide the price for iron ore this year. The talks are continuing despite the arrests and investigations, the paper said.Rio Tinto still has four employees detained. The Shanghai-based staff have been held since last week on spying charges. Stern Hu, Rio Tinto's iron ore marketing chief in China and one of those arrested, is an Australian citizen.The Rio employees are accused of bribery to obtain summaries of the negotiators' meetings, according to Chinese news reports.Australian Treasurer Wayne Swan has called for Hu's case to be handled quickly as anger is growing in Australia over his detention."As the Foreign Minister has made clear, we may well be in for the long haul in regard to this case. Australian officials will continue to press Chinese authorities for further detail on the reasons for Mr Hu's detention and reiterate Australia's view that his case should be handled expeditiously," he said.