Cofidis rider Remy Di Gregorio was arrested on Tuesday along with two other people suspected of supplying him with banned substances.
The official said the preliminary charges against the three could include the organized offer or sale to an athlete of a substance banned in competition, the organized administration, solicitation or import of the substance, and violating rules against trafficking in or use of poisonous substances.
The official spoke on condition of anonymity because he was not authorized to speak about an ongoing investigation.
Di Gregorio has been provisionally suspended by his team pending the outcome of an investigation.
The 26-year-old was in 35th place after Monday's ninth stage. The Marseille native turned pro in 2005 with French team Francaise des Jeux, and was once considered one of the most promising young French riders.
"After being legitimately floored by this event, the riders have recovered," said Cofidis manager Yvon Sanquer at the stage start in Macon in eastern France on Wednesday. "They are ready to give their best and we will now be fighting for the best young rider's white jersey for Rein Taaramae."
Di Gregorio's teammates were not available for questions regarding the investigation.
AP Sports Writer Samuel Petrequin in Macon contributed.