Investigations iof Rio Tinto employees accused of corporate espionage by the Chinese Government will continue for another month, reports suggest.

News agency Reuters said a defence lawyer on the case said four employees, detained in August for holding state secrets before iron ore negotiations between Rio, Vale and BHP Billiton and Chinese steel mills, could face two months more of investigations if more extensions were granted.

An official at China’s Shougang Steel was also detained and charged with stealing commercial secrets. It is feared, however, that China’s more serious state secrets charge could be brought into use if broadly applied to the case.

The case has damaged trade ties between Australia and China, and raised concerns over China’s use of laws regarding ‘sensitive’ information.