PARIS — French police questioned former International Monetary Fund chief Dominique Strauss-Kahn all day Tuesday in a probe into a suspected hotel prostitution ring.

Strauss-Kahn, a one-time French presidential hopeful whose chances were derailed by a sexual assault accusation in New York, arrived at the police station in the northern city of Lille for a prearranged morning appointment. He hadn’t emerged by Tuesday night, and French media reported that he would be held overnight.

French law permits police to question Strauss-Kahn for up to 96 hours with a judge’s approval.

Police are probing a suspected prostitution ring in France and 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 in Washington, D.C.

Two businessmen 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.

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

Strauss-Kahn, 62, lived in Washington while he was head of the IMF before resigning in May after he was charged by New York police with making a hotel maid perform oral sex. The charges were later dropped.

Strauss-Kahn’s name surfaced in the investigation last fall, and his lawyer has asked that his client 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.

“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.

Strauss-Kahn has been married for 20 years to journalist Anne Sinclair.

The case in France is unconnected to the attempted-rape accusations in New York.