SHANGHAI — The Chinese authorities have detained or questioned at least seven Chinese steel industry executives in a broadening corruption investigation connected to the detentions last week of four employees of the mining giant Rio Tinto, the state-controlled news media reported Monday.

The investigation, which began with accusations that the four Rio Tinto workers had conspired to steal state secrets, has rapidly widened, according to accounts on government Web sites and Chinese news media. It now includes accusations of widespread bribery in business dealings, as well as allegations that the four workers paid for detailed government trade and manufacturing data to give Rio Tinto executives an edge in iron-ore negotiations with Chinese state-controlled steelmakers.

The reports said that senior managers at five steel factories were giving the authorities information. Those being questioned include shippers, traders and steel-mill managers. A week ago, an executive at Shougang Steel in Beijing, one of the country’s biggest steelmakers, was detained.