China, after detaining four Rio Tinto mining company employees on spying charges, has expanded its investigation against seven steel industry executives.

The executives have either been detained or questioned as part of a broadening corruption probe, The New York Times reported Tuesday, quoting state-controlled Chinese news media.

While the Rio Tinto workers have been accused of conspiring to steal state secrets, the new investigation includes accusations of widespread bribery in business dealings, said reports on government Web sites and local media. There were also allegations the four Rio Tinto workers paid for detailed government trade and manufacturing data to give their executives an edge in iron ore negotiations with Chinese state-controlled steelmakers, the Times said.

The allegations said senior managers at five steel factories were giving the authorities information.

The Times said Rio Tinto officials declined comment Monday and a spokesman for the China Steel and Iron Association was not available for comment. However, experts on China's large steel and iron ore industry were quoted as saying corrupt practices -- including exchange of market data now designated as state secrets by the Chinese government -- have gone on for years.

China is the world's largest producer of steel and Rio Tinto is one of its biggest suppliers of iron ore, the Times said. Government officials denied politics was involved, saying the Rio Tinto case will not hurt Chinese-Australian relations.