Australian cyclist Michael Rogers has been provisionally suspended by the UCI after it emerged he had tested positive for the banned substance clenbuterol during October's Japan Cup.
The 33-year-old Saxo-Tinkoff rider, who is a three-time world time-trial champion, will now await the outcome of an investigation by the Australian anti-drug authorities.
The result of the test means the Rogers' former team, Sky Procycling, are under increasing scrutiny after British rider Jonathan Tiernan-Locke, who is still with the team, was also suspended recently after an anti-doping violation.
A statement from Rogers' team read: "Michael Rogers immediately informed Saxo-Tinkoff's management about the notification from the UCI.
"The Australian explained to the team management that he never ingested the substance knowingly nor deliberately and fears that the adverse analytical finding origins from a contaminated food source.
"Michael Rogers participated in Tour of Beijing the week before the Japan Cup and travelled directly from China to Japan."
Two-time Tour de France winner Alberto Contador, now Rogers' team-mate at Saxo-Tinkoff, also tested positive for clenbuterol during the 2010 Tour. The drug helps to burn fat and build muscle.
Rogers left Team Sky, who have a strict anti-doping policy, for Saxo-Tinkoff in 2012 after he was named in evidence given during the trial of disgraced American Lance Armstrong.