Judge Jean-Michel Gentil questioned the former French leader in November for 12 hours concerning evidence given by Bettencourt's former accountant, Claire Thibout, BFM-TV reported.
Magistrate Jean-Michel Gentil, who leads the inquiry, unexpectedly summoned Mr Sarkozy for a face-to-face encounter with Mrs Bettencourt's butler, Pascal Bonnefoy, in the city of Bordeaux.
"This search, as expected, proved to be futile given that all required elements had been sent to the magistrate (Jean-Michel Gentil) a fortnight ago, " Herzog said.