Chinese authorities have backed down from accusing four Rio Tinto executives of espionage but restated the charges yesterday to include stealing commercial secrets and bribery.

Official news agencies said that investigators had discovered that the four employees of the Anglo-Australian mining group had obtained commercial secrets about China’s steel and iron industries through “improper means and were involved in bribery”.

Rio Tinto said that its employees were innocent and that it would fight any charges.

China’s decision to remove allegations of “stealing state secrets” may help to defuse diplomatic tensions between Australia and China over the incident. Stern Hu, the head of Rio’s iron-ore negotiations, has dual Australian-Chinese citizenship.

Sam Walsh, the chief executive of Rio’s iron ore division, said: “From all the information available to us, we continue to believe that our employees have acted properly and ethically in their business dealings in China. The issue of the arrest warrant is of great concern. We respect the Chinese legal system and we hope to see a transparent process for our employees, including access to legal representation.”

Mr Hu and the three Chinese nationals working for Rio were detained last month amid contentious ore price talks with Chinese steel mills.

Chinese media had previously reported that Mr Hu had paid bribes in exchange for information on China’s negotiating stance in those talks. Some reports also said that Mr Hu’s actions amounted to stealing state secrets and there were fears that Chinese prosecutors could seek the death penalty for espionage. The restated arrest warrant issued yesterday is for lesser charges, but Mr Hu and his colleagues could still face up to seven years in prison.

There has been speculation that the arrests were politically motivated, particularly as Rio recently walked away from a $19.5 billion investment by Chinalco, the Chinese state-owned metals group.

Australia has expressed concern over the handling of the case and fears that Mr Hu may not receive a fair trial.

Fu Ziying, China’s deputy commerce minister, said: “We believe Chinese judicial organs will make a fair ruling on the case based on the facts and in accordance with law. There is no question about that.”

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