They said the prosecutor's office could then put the Brazilian, who was arrested on Tuesday morning at his home in Cassis, under formal investigation.
French police sources said Brandao was due to meet the 23-year-old woman, who has accused him of rape, later on Wednesday.
"He admits to sexual intercourse with this woman but not in the conditions she describes," Brandao's lawyer, Patricia Clusan, told Reuters. "To him, this intercourse had nothing abnormal because she agreed to it."
The woman's complaint, however, could have been withdrawn, according to a source close to the incident.
"I cannot either confirm or deny this information because I have not had access to the file," Clusan said.
"Even if the complaint would be withdrawn, the prosecutor's office could still decide to continue with the procedure."
The woman accused Brandao, 30, of raping her at a motorway rest area after he offered to drive her home from an Aix-en-Provence night club last week.
Police officers have visited Marseille's training ground to question other players who may have met the young woman at the night club, a source close to the investigation said.
"Everybody is being questioned as part of the investigation," Marseille coach Didier Deschamps told reporters.
"There is an ongoing investigation and it is a private matter. High level athletes are public figures. There is what they do on the pitch and what they do off the pitch. They are accountable for what they do and say."
Brandao joined from Shakhtar Donetsk in 2009, netting eight goals in 30 Ligue 1 appearances last season.
