Sarkozy is being held at Nanterre, outside Paris, while investigators look into whether he made promises to a high-ranking judge in exchange for information about an ongoing investigation into alleged illegal campaign funding.
The 59-year-old was president from 2007 to 2012 and was expected to run for the presidency again in 2017.
Multiple judges have already been questioned as part of the probe, as well as Sarkozy's lawyer Thierry Herzog.
"The justice system is investigating and will follow this through to the end. Nicolas Sarkozy can face justice just like anyone else," government spokesman Stephane Le Foll told the BBC.
The ex-president claims that the allegations against him are politically motivated.
The mayor of Nice, Christian Estrosi, tweeted: "Never has any former president been the victim of such treatment, such an outburst of hatred."
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