Tour de France winner Alberto Contador has revealed he has tested positive for a banned substance.
Contador, who topped the Paris podium for the third time in July, tested positive for clenbuterol during the final rest day in this year's tour.
The Spaniard's spokesperson claimed the presence of the substance was due to "food contamination".
Contador will speak to the world's media on Thursday after he himself revealed details of the failed test.
"From the time of the first communication ... Alberto Contador alleged food contamination as the only possible explanation," read a media release on his behalf.
"The experts consulted so far have agreed also that this is a food contamination case, especially considering the number of tests passed by Alberto Contador during the Tour de France."
Cycling's governing body, the UCI, has provisionally suspended the 27-year-old former Astana rider.
"The concentration found by the laboratory was estimated at 50 picograms (or 0,000 000 000 05 grams per ml)," read a UCI statement.
The amount is 400 times less than what the anti-doping laboratories accredited by the World Anti-Doping Agency must be able to detect.
The statement continued: "In view of this very small concentration and in consultation with WADA, the UCI immediately had the proper results management proceedings conducted including the analysis of B sample that confirmed the first result.
"The rider, who had already put an end to his cycling season before the result was known, was nevertheless formally and provisionally suspended as is prescribed by the World Anti-Doping Code."