International Monetary Fund chief Christine Lagarde has said the decision to formally investigate her over negligence claims was "without basis".
In a statement after a fourth round of questioning before magistrates, Lagarde said she was returning to work in Washington later in the day.
"After three years of proceedings, dozens of hours of questioning, the court found from the evidence that I committed no offence, and the only allegation is that I was not sufficiently vigilant," Lagarde said.
International Monetary Fund chief Christine Lagarde has been placed under formal investigation for negligence relating to a long-running political fraud case, an unnamed source has told Reuters.
Lagarde will appeal the French magistrates' decision to place her under formal investigation, saying the allegation of negligence was unfounded, the source stated.
The inquiry into French businessman Bernard Tapie has embroiled several
of former president Nicolas Sarkozy's cabinet members, including Lagarde, who was finance minister.
Tapie was awarded €403 million (£321 million) in a 2008 arbitration payment
under Sarkozy's presidency to settle a dispute with the now-defunct state-owned bank Credit Lyonnais over a share sale in 1993.
The head of the IMF, Christine Lagarde, has firmly denied suggestions that she may become the next president of the European Commission.
Speaking at an IMF press conference in London, Ms Lagarde insisted: "I'm not a candidate and the reason I'm not a candidate is I have a job and it's a job I happen to think is rather important at the moment."
She also made a reference to the 70th anniversary of the D-Day landings, saying: "When you start something you've got to finish the job, that's what a few people did 70 years ago, thank goodness."