French police questioned President Sarkozy's longtime friend and adviser Brice Hortefeux on Friday, in connection with the so-called Karachi affair, in which two of Sarkozy's closest allies are already implicated.
He was interviewed over a phone call he made to a suspect in the Karachi affair, to warn him that his estranged wife had been talking to investigators.
The call to Thierry Gaubert, who was also a close aide to Sarkozy before he became president, was intercepted by investigators and leaked to the media.
Gaubert's wife had told police that her husband made trips to Switzerland in the 1990s to collect suitcases full of cash to finance Edouard Balladur's unsuccessful presidential campaign.
Nicolas Sarkozy was campaign spokesman for Balladur at the time, and also budget minister.
It's alleged that the Swiss money was kickbacks from arms sales to Pakistan, and that a 2002 bombing in Karachi, which killed 11 French engineers, was revenge for the cancellation of bribes which had been secretly promised to Pakistani officials.
Hortefeux is accused of breaching the confidentiality of a judicial investigation, but he said after Friday's interview with police that he was able to demonstrate that he "knew nothing of the contents of the judicial investigation."
He was released without charge after three hours and issued a statement saying he had been questioned at his own request, as a witness.
Gaubert has already been charged and is under investigation.