PARIS (AFP) - French police have detained a judge and a lawyer for questioning in connection with a corruption case linked to IMF chief Christine Lagarde, judicial sources said on Tuesday.

The judge, magistrate Pierre Estoup, was detained on Monday by investigators probing a massive state payout to a disgraced tycoon in 2008, when Ms Lagarde was finance minister.

The International Monetary Fund chief was questioned for two days last week about the 400 million euro (S$654 million) payout to controversial business figure Bernard Tapie, but she avoided charges and was instead named an "assisted witness".

Mr Estoup was one of the three judges who presided over the arbitration panel that granted the payment to Tapie, which followed a dispute between the businessman and partly state-owned bank Credit Lyonnais over his 1993 sale of sports group Adidas.

The panel upheld his claim that Credit Lyonnais had defrauded him by intentionally undervaluing Adidas at the time of the sale and that the state, as the bank's principal shareholder, should compensate him.

Investigators are probing whether Mr Tapie received favourable treatment in return for supporting ex-president Nicolas Sarkozy, Ms Lagarde's then boss, in the 2007 presidential election.

The sources said Mr Estoup's detention was based on his failure to reveal a former professional relationship with one of Mr Tapie's lawyers in the case, Maurice Lantourne.

Mr Lantourne was himself detained for questioning on Tuesday, the sources said.

Ms Lagarde has denied any wrongdoing in the case and the IMF board has expressed confidence in her leadership.

While Ms Lagarde avoided being charged following her questioning, her "assisted witness" status means she could still face further questions - and possibly charges - at a later stage.