Former International Monetary Fund chief Dominique Strauss-Kahn was being held for questioning on Tuesday by French police investigating a suspected hotel prostitution ring.

Strauss-Kahn, a one-time French presidential hopeful whose chances were derailed by a sexual assault accusation, arrived at the police station in the northern city of Lille around 0800 GMT, an Associated Press reporter saw. French law permits police to question Strauss-Kahn for 48 hours, renewable once with a judge’s approval.

Police are probing a suspected prostitution ring in France and neighbouring Belgium that has implicated police and other officials. They have questioned prostitutes who said they had sex with Strauss-Kahn during 2010 and 2011 at a luxury hotel in Paris, a restaurant in the French capital and also in Washington, DC.