Detailed information of Chinese steel mills was found in computers of Rio Tinto's Shanghai office, local media reported Monday.
Four employees of Australian iron ore supplier Rio Tinto were detained in Shanghai on July 5 on charges of espionage.
An insider said that Rio knew almost every detail of some Chinese steel companies, all of which signed long term sales contracts with Rio.
Information in Rio's computers includes the outputs, sales, purchasing plans, raw material stocks and schedules of production.
"Even presidents of these companies may not have such detailed information," the insider said.
Tan Yixin, a senior executive of China's major steel maker Shougang Group, was detained July 7 in Beijing for alleged "commercial crimes". Tan was in charge of the company's import and export business of iron ore.
Many employees of foreign iron ore suppliers used to work in Chinese steel mills and they knew details of the firms, according to insiders.
"Foreign iron ore suppliers also bribed executives from Chinese steel makers during holidays and festivals," an insider said.