UPDATE 1-China formally arrests Rio Tinto employees

By Chris Buckley

BEIJING, Aug 12 (Reuters) - Chinese prosecutors have formally arrested four employees of mining giant Rio Tinto (RIO.AX) (RIO.L) on suspicion of violating commercial secrets and taking bribes, the official Xinhua news agency reported on Wednesday.

Australian national Stern Hu and three Chinese employees of the Anglo-Australian company -- Liu Caikui, Ge Minqiang, and Wang Yong -- are suspected of "using improper means to obtain commercial secrets about our country's steel businesses", Xinhua cited prosecutors in Shanghai as saying.

The report said the procuratorate, or state prosecutors, also approved their formal arrest on suspicion of taking bribes.

"The procuratoratial organ conducted investigations and believes that it has evidence that the four, including Stern Hu, are suspected of the above crimes," said the report.

The decision means Chinese prosecutors are officially looking at whether they have the evidence to bring the four to trial.

Previous reports had suggested the men may be under investigation for violating state secrets. But there was no mention of that more serious crime in this report.

Rio Tinto had no immediate response to the report, but it has previously said that the four detained employees did nothing improper.

Xinhua said that in recent days Chinese steel executives have also been formally arrested on suspicion of "providing commercial secrets" to Stern Hu.

(Reporting by Chris Buckley; Editing by Jeremy Laurence)