French police have released former International Monetary Fund chief Dominique Strauss-Kahn after two days of questioning about a prostitution ring.

On Wednesday, Strauss-Kahn was quickly driven away in a sedan with dark tinted windows from the police station in the northern city of Lille.

Police say Strauss-Kahn’s name came up during their probe into a prostitution ring at hotels in Lille and Paris, which also implicates a police official. Investigators are trying to determine if he knew women entertaining him at hotels and restaurants in Paris and Washington, D.C. were prostitutes.

Strauss-Kahn’s lawyer says he admitted to having sex with the women, but says he was unaware they were prostitutes.

Two businessmen with ties to the 62-year-old Strauss-Kahn are accused of running a prostitution ring and misusing funds. Prosecutors are trying to determine if prostitutes were paid money fraudulently taken from a company.

Paying a prostitute is not illegal in France. However, using ill-gotten funds could bring charges.

Strauss-Kahn could learn next month if judges will formally charge him in the case.

Strauss-Kahn resigned from the IMF last May after he was charged with sexually assaulting a hotel maid in an upscale New York hotel. U.S. prosecutors dropped the case a few months later after concluding the maid’s testimony was unreliable.

Strauss-Kahn still faces a civil lawsuit filed by the hotel maid in the United States.

Political observers say the U.S. case derailed Strauss-Kahn’s expected run for president of France this year.