Nairo Quintana has claimed no illegal substances were found when French police searched his hotel room during the Tour de France as part of an anti-doping investigation.
The Colombian, 30, said only “legal vitamin supplements” were seized.
The public prosecutor’s office in Marseille has opened a preliminary investigation and Quintana said he was voluntarily questioned by police.
“I do not have, and have never had, anything to hide,” he added.
The former Giro d’Italia and Vuelta a Espana winner rides for French team Arkea-Samsic and their hotel rooms were searched after stage 17 of this year’s Tour, in Meribel on 16 September.
Marseille prosecutor Dominique Laurens said on Tuesday two people were taken into custody who were part of the “close entourage of the main rider”, without naming him.
Laurens added the investigation was targeting a “small part of the team” and said the search led to the “discovery of many health products, including drugs and especially a method that can be qualified as doping”.
In a statement Quintana said: “That day, the authorities entered my room and seized vitamin supplements that were perfectly legal, although perhaps unfamiliar to the French authorities.
“This is the main reason why it takes time for everything that happened to be fully clarified. To avoid any doubt, I would like to confirm that no doping substances were ever found.”
On Monday, an Arkea-Samsic statement said the investigation was not focused “directly” on the team and involved “a very limited number of riders, as well as their close entourage, not employed by the team”.
The team added that if wrongdoing was discovered it would “immediately dissociate itself from such acts and take without delay the necessary measures”.
Quintana added: “I would also like to clear up a misunderstanding: I have never consulted assistants or staff who were not part of the team, neither during the recent Tour, nor during any other previous race.
“It must be stressed that I have not been the subject of any accusation by the authorities.”
Arkea-Samsic was given a wildcard entry to the Tour, which finished last Sunday, and was led by Quintana.
The Colombian – who has finished on the podium in three previous Tours – suffered a crash on stage 13 and then cracked on the Grand Colombier two days later before finishing 17th overall.
