Prokhorov, a co-owner of Interros, which manages key assets in Russia's nickel, platinum and gold mining sectors, was apprehended Tuesday in the Courchevel ski resort, in the French Alps, when Lyons police raided several hotels in an operation targeting prostitution among minors.
"A total of 26 people, most of them Russians, were detained in the operation, aimed against prostitution involving minors," a source in the Lyons Prosecutor's Office said. "From Courchevel, the detainees were taken to Lyons, where 15 people were released after questioning while the other 11, including Prokhorov, were left in custody."
French police said Prokhorov was questioned as a witness and not as a suspect.
Prostitution itself is legal under French law, but profiting from the earnings of prostitutes and prostitution involving minors are illegal.
Interros spokesperson Yelena Kovaleva said earlier the company's top management has not received any official notification of Prokhorov's arrest, and that they view it as a "mistake." She said Prokhorov is currently on vacation, and will return to work next Monday.
Prokhorov, a Courchevel regular, is said to throw lavish parties every time he comes to the resort, inviting along dozens of young prostitutes, according to Russian business daily Vedomosti.
The tycoon owns a 54.8% stake in the Russian company Norilsk Nickel, the world's largest producer of nickel and platinum, and 51% in Polyus Zoloto, the country's No. 1 gold mining company.
