The Real Madrid and France star arrived at the police station in Versailles, near Paris, early on Wednesday and was placed in detention, the local prosecutor confirmed, without giving further information.
Investigators are trying determine the extent to which Benzema was aware of the intimate video featuring Valbuena, which found its way into the hands of blackmailers.
According to the source, Benzema mentioned the sextape to Valbuena during a meeting of the French team in early October.
It is thought one of Benzema's relatives was contacted by the suspected blackmailers with a view to involving the footballer in their scheme, the source said.
Police are seeking to determine whether he was teasing Valbuena when he mentioned the tape, or trying to make him pay the blackmailers.
The blackmail case was first opened in late July, and carries a potential prison sentence of five years.
The three suspected blackmailers, who are friends with several footballers, were charged and placed in detention in October.
The case also saw four other people arrested last month, including former French international footballer Djibril Cissé.