France's ex-president Nicolas Sarkozy was being held for questioning over alleged attempt to pervert the course of justice, according to legal sources.
Sarkozy, who was president from 2007 to 2012, is the first former head of state to be quizzed in police custody. He arrived in Nanterre, west of Paris, to be questioned after his lawyer Thierry Herzog was held on Monday.
Under French law, suspects in criminal cases can be held in custody for up to 48 hours before they must be either charged or released.
Police are trying to ascertain whether Sarkozy tried to obtain inside information from one of the judges about the progress of another probe concerning allegations that his 2007 election campaign was financed by former Libyan dictator Muammar Gaddafi with up to 50 million euros and that he was alerted that his mobile phone had been tapped.
Sarkozy always rejected any accusations in connection with the Gaddafi case. Judges obtained an authorisation to tap phones belonging to a former president and are now trying to find out whether Sarkozy had promised a prestigious role in Monaco to a top judge in exchange for information on the case.
The former president could be charged for "influence peddling" in French law with a maximum prison sentence of 10 years, if convicted.
The latest development could be a fatal blow to Sarkozy's possible bid to presidency in 2017.