Sarkozy, president from 2007 to 2012, was seen by a Reuters photographer leaving his home in Paris with his lawyer in a car, then entering the offices of investigators who had placed him in custody and started questioning him on Tuesday.
That start of a second day of questioning was confirmed by a second source close to the inquiry who said the session started at 8 a.m. local time (0700 GMT).
Neither Sarkozy nor his lawyers have commented publicly about the latest development in an inquiry that began five years ago. But the 63-year-old has in the past called the allegations "grotesque" and a "manipulation".
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