The Real Madrid striker appeared before a judge in Versailles after being held in custody overnight.
His lawyer says he played “no part” in an alleged attempt to extort money from fellow French international Mathieu Valbuena.
The two men reportedly had an exchange during a training session.
According to French media, Mr Benzema mentioned the tape to the midfielder during a national team training session at Clairefontaine in early October.
A source close to inquiry, quoted by told AFP news agency, said the 27-year-old star told investigators on Thursday he had approached Mr Valbuena about the tape on behalf of “a childhood friend”.
France coach Didier Deschamps left both players out of his squad selected on Thursday for matches against Germany and England later in November.
‘Nothing to hide’
The prosecutor’s office earlier confirmed that Mr Benzema was now under formal investigation for complicity in attempted blackmail and participation in a criminal conspiracy.
When a suspect is placed under formal investigation, he or she is then examined by a judge, who determines whether there is sufficient evidence for the suspect to be charged.