(Reuters) - Former IMF chief Dominique Strauss-Kahn is to be questioned next week by police investigating an alleged prostitution ring in Lille, northern France, a police source said.

The former finance minister, who left the International Monetary Fund (IMF) last May to face attempted rape charges in New York that were later dropped, had publicly demanded to be interviewed in the separate Lille case.

Dominique Strauss-Kahn (Reuters)

Strauss-Kahn has been summoned for 3 am EST on Tuesday, the source said, confirming a report in La Voix du Nord newspaper yesterday. He is to be taken into custody and questioned for up to 48 hours, according to the regional daily.

Messages left for Strauss-Kahn’s Paris attorney were not immediately returned.

Once seen as a likely contender against French President Nicolas Sarkozy in upcoming elections, Strauss-Kahn bowed out of public life after his US arrest on allegations that he attempted to rape a Guinean hotel maid.

The maid, Nafissatou Diallo, is now pursuing him in a civil action after prosecutors dropped criminal charges.

Separate attempted-rape accusations by a Parisian writer were also shelved by French police on October 13 – three days before Strauss-Kahn’s name surfaced again in the Lille investigation.

The probe is focused on a prostitution ring that allegedly supplied women to clients of the city’s luxury Carlton hotel. Local businessmen and a police commissioner are among several people arrested so far.

French construction firm Eiffage dismissed an executive suspected of using company funds to hire prostitutes, who allegedly took part in sex parties with Strauss-Kahn in Paris and Washington.

Strauss-Kahn believed he was participating in swingers’ parties and had no reason to suspect that the women were prostitutes, his lawyer Henri Leclerc has previously said. Consorting with prostitutes is legal in France.