French investigators are studying accusations that Dominique Strauss-Kahn may have been involved in a rape during a sex party in a Washington hotel in 2010, while he was chief of the International Monetary Fund, a judicial official said Friday.

Strauss-Kahn, via his lawyers, denied any violence and said he's the subject of a public "lynching campaign." The prominent economist, once a top contender for France's presidency, has seen his career and reputation crumble since he was accused of sexual assault in a New York hotel a year ago.

Investigating judges in the northern French city of Lille have asked for prosecutors' permission to broaden a suspected prostitution probe to examine claims of rape during an orgy in Washington in December 2010, said an official at the Lille prosecutor's office.

The prosecutor's office will decide next week whether to expand the investigation, the official said. The official was not authorized to be publicly named because of prosecutor's office policy.

Strauss-Kahn is already a target in the Lille prostitution probe, which has mushroomed over the past year into a nationwide scandal. He is facing preliminary charges of alleged aggravated pimping, based on accusations by other people questioned in the investigation.

He denies those charges, acknowledging he was involved in "libertine" activity while saying that he was unaware of anyone being paid for sex.

The Lille prosecutor's office gave no details of the U.S. rape accusations.

French daily Liberation reported Friday that two Belgian prostitutes questioned in the Lille probe described Strauss-Kahn as using violence during sex and forcing one of them to have anal sex despite her protests.

Bill Miller, a spokesman for the U.S. attorney's office in Washington, declined Friday to comment on the allegations. A spokeswoman for Washington's Metropolitan Police Department had no immediate comment.

Strauss-Kahn's lawyers said no legal complaint has been filed about the suspected incident.

"Strauss-Kahn absolutely contests having committed the slightest violence of any nature, and notes that the declarations made by the young women are contradictory," lawyers Frederique Beaulieu and Richard Malka said in a statement.

They noted that the accusations surfaced two days before France's presidential elections. Strauss-Kahn has reportedly said the sex-related accusations against him were part of an effort to discredit him and keep him out of France's presidential race, where he once was considered a leading challenger to President Nicolas Sarkozy.

Strauss-Kahn is facing a trial in New York over a lawsuit by a hotel maid who accused him of sexual assault in May 2011. A judge ruled this week that the trial can go forward despite Strauss-Kahn's claim that he had diplomatic immunity.

A French writer had accused Strauss-Kahn of sexually assaulting her during an interview in 2003, but prosecutors ruled last year that too much time had passed to pursue her complaint.