Dominique Strauss-Kahn, the former chief of the International Monetary Fund (IMF), is being questioned by French police as part of an investigation into a suspected prostitution ring.br br A prosecutor on Tuesday said Strauss-Kahn was being questioned in the northern French city of Lille as a suspect over alleged cross-border prostitution ring in France and neighbouring Belgium that has implicated police and other officials.br br Investigators are seeking to discover if prostitutes were paid using corporate funds from a large French construction company.br br Al Jazeera's Emma Hayward reports from Paris.