Former IMF chief Dominique Strauss-Kahn was released from a French police station on Wednesday after two days of questioning about an alleged illegal prostitution ring.
The 62-year-old former Socialist minister was driven away by car under a police motorcycle escort from the station in the northern city of Lille, where dozens of journalists had gathered.
Prosecutors said Strass-Kahn, once considered a front-runner to become the next president of France, would be summoned to appear again before investigating magistrates in March over a series of sex parties.
He was freed after being detained for about 32 hours for questioning by police on charges of "abetting aggravated pimping by an organised gang" and "misuse of company funds".
During his interrogation, Strauss-Kahn told investigators he did not suspect women he met at orgies were prostitutes, as they were introduced to him by senior police officers, a source close to the probe said.
When he next talks to authorities, Strauss-Kahn will either be interviewed under caution as a witness or to face charges linked to prostitution and corruption, the source said.
Frederique Baulieu, one of Strauss-Kahn's lawyers, said his client was "perfectly satisfied" to have been heard by investigators and that he had responded to the questioning in a "calm" manner.
He was also to be quizzed by France's police internal affairs department, the IGPN, which is conducting a separate inquiry into a senior officer, Commissioner Jean-Christophe Lagarde, who has been charged with pimping.
Strauss-Kahn, who until last year seen as the likely candidate to replace Nicolas Sarkozy as president of France, was taken into custody on Tuesday.
Under French law, aggravated organised pimping carries a prison term of up to 20 years and profiting from embezzlement five years and a fine.
Investigating magistrates want to know whether he was aware that women who entertained him at parties in restaurants, hotels and swingers' clubs in Paris and Washington were paid prostitutes.
They will also ask whether Strauss-Kahn knew the escorts were paid with funds allegedly fraudulently obtained from a public works company by his hosts.
Paying a prostitute is not illegal in France, but profiting from vice or embezzling company funds to pay for sex can lead to charges.
The former managing director of the International Monetary Fund acknowledges having an uninhibited sex life, but rejects any role in pimping or corruption and has indicated he will deny any criminal wrongdoing.
Lawyer Henri Leclerc has said his client may not have known he was with prostitutes as "in these parties, you're not necessarily dressed. I defy you to tell the difference between a nude prostitute and a nude woman of quality."
Two businessmen, Fabrice Paszkowski, a medical equipment tycoon with ties to Strauss-Kahn's Socialist Party, and David Roquet, former director of a local subsidiary of building giant BTP Eiffage, have already been charged.
The pair are alleged to have links to a network of French and Belgian prostitutes centred on the Carlton Hotel in Lille, a well-known meeting place of the local business and political elite in a city run by the Socialist Party.
In all, eight people are facing trial in connection with the "Carlton affair", including three executives from the luxury hotel itself, a leading lawyer and the police chief, Lagarde.
The last of the sex parties is said to have taken place during a trip by a group from Lille to Washington between May 11 and 13 last year.
One day later, on May 14, Strauss-Kahn was arrested in New York following allegations that he had subjected chambermaid Nafissatou Diallo to a brutal sexual assault in his hotel suite.
The case against him eventually collapsed when prosecutors began to doubt Diallo's credibility as a witness. Strauss-Kahn returned home to France, only to face further investigation and scandal.
First, 32-year-old French writer Tristane Banon accused him of attempting to rape her in 2003. Prosecutors decided there was prima facie evidence of a sexual assault, but ruled that the statute of limitations had passed.
Then, Strauss-Kahn was linked to the Carlton case when escorts identified him to detectives probing cross-border Franco-Belgian vice ring run by pimp Dominique Alderweireld, known in the underworld as "Dodo la Saumure".