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

Strauss-Kahn arrived at the police station in the northern city of Lille around 8 a.m. local time. He was to remain in police custody overnight.

Under French law, police can detain him for 48 hours for questioning and renew that period once with a judge's approval before deciding whether to lay charges.

Police are probing a suspected prostitution ring in France and neighbouring Belgium that has implicated police and other officials.

Prostitutes say they had sex with Dominique Strauss-Kahn during 2010 and 2011 at a luxury hotel in Paris, a restaurant in the French capital and also in Washington, D.C. (Jason Lee/Reuters)

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, D.C. Strauss-Kahn lived in the U.S. capital while he was head of the IMF before resigning his position in May.

Two men with ties to Strauss-Kahn have been put under preliminary investigation in France on charges including organizing a prostitution ring and misuse of corporate funds.

Strauss-Kahn's name surfaced in the investigation last fall and his lawyer has asked that Strauss-Kahn be allowed to tell his side of the story. One of Strauss-Kahn's lawyers has said that the former French presidential hopeful never knew that the women at orgies he attended were prostitutes.

"He could easily not have known, because as you can imagine, at these kinds of parties you're not always dressed, and I challenge you to distinguish a naked prostitute from any other naked woman," Henri Leclerc told French radio Europe 1 in December.

French newspapers have dubbed the investigation "The Carlton Affair" after the name of the expensive Lille hotel where some of the meetings took place.

Investigators are seeking to discover if prostitutes were paid using corporate funds from a large French construction company.

It is Strauss-Kahn's latest run-in with police over alleged sexual misconduct.

Strauss-Kahn was charged by New York police in May with making a hotel maid perform oral sex. The one-time French presidential hopeful has said the sexual encounter was "inappropriate" but not violent.

New York prosecutors dropped the case against him in August because the woman had undercut her credibility by lying about her background and changing her account of her actions right after the alleged attack. She says she was truthful about the encounter and is pursuing her claims in a lawsuit.

In a separate case last October, French prosecutors refused to pursue an allegation by a young French writer of attempted rape by Strauss-Kahn.

The Paris prosecutor's office dropped the investigation into writer Tristane Banon's claim that Strauss-Kahn tried to rape her during a 2003 interview for a book the then-23-year-old was writing, saying they couldn't send him to trial because it happened too long ago.