One of three men arrested as part of an investigation into doping has been released, but Cofidis\' Tour de France rider Remy Di Gregorio and a 75-year-old man are to remain in custody, a police source confirmed on Wednesday. Di Gregorio, 26, was arrested following a police raid at his team\'s hotel in Bourg-en-Bresse, several miles outside Macon in eastern France on Tuesday as part of an investigation into the organised trafficking of doping substances. He was brought to Marseille for further questioning by investigating magistrate Annaick Le Goff, along with the two other unidentified men, who are suspected of \"having dealings\" with Di Gregorio. The two men could be presented before Judge Le Goff later Wednesday or on Thursday after being held in custody for 48 hours. According to the same source, the inquiry into the trafficking of doping substances was opened in June 2011 and initially focused on Di Gregorio\'s former Kazakh team Astana. The inquiry never reached a conclusion but the case moved forward following a series of telephone tapping, the sources said. Tests are now underway to determined if the products found in a car in Bourg-en-Bresse are of a doping nature. If found guilty of drug trafficking the accused face a maximum seven years in jail and a 150,000-euro fine.