The latest developments are seen as a blow to Mr Sarkozy's attempts to stand again for the presidency.French ex-President Nicolas Sarkozy has been detained for questioning over alleged influence peddling, bbc reports.
The decision to detain him at Nanterre, near Paris, is an unprecedented step against a former president.
Mr Sarkozy's lawyer was questioned on Monday on suspicion of seeking inside information about a case against the former leader.
The latest developments are seen as a blow to Mr Sarkozy's attempts to challenge for the presidency in 2017.
Investigators are trying to find out whether Mr Sarkozy, who was president from 2007 to 2012, had promised a prestigious role in Monaco to a high-ranking judge in exchange for information.
Gilbert Azibert, one of the most senior judges at the court of appeal, was also called in for questioning on Monday.