French police have searched the Paris apartment of IMF chief Christine Lagarde, as they investigate her role in awarding financial compensation to businessman Bernard Tapie in 2008.
As finance minister, she referred his long-running dispute with bank Credit Lyonnais to an arbitration panel, which awarded him 400m euros (£340m) damages.
Mr Tapie was a supporter of ex-President Nicolas Sarkozy.
Critics say she abused her authority but Ms Lagarde denies any wrongdoing.
"This search will help uncover the truth, which will contribute to exonerating my client from any criminal wrongdoing," Ms Lagarde's lawyer, Yves Repiquet, told the Reuters news agency.
The BBC's Christian Fraser in Paris says investigators suspect Mr Tapie was granted a deal in return for his support of President Sarkozy in the 2007 election.
There is speculation in France that Ms Lagarde could yet be placed under formal investigation in this case, he adds.
The origins of the case date back 20 years.