Luxembourg rider Frank Schleck has been removed from the 2012 Tour de France after failing a drugs test - the second time this year's event has been hit by reports of substance abuse.
Schleck, has been removed by his team, RadioShack-Nissan, after testing positive for the banned diuretic xipamide on 14 July. The drug, which combats water retention, helps users to lose weight - potentially a major advantage to riders during the Tour's mountain stages.
Schleck, says he "categorically denies" taking a banned substance, and has demanded further analysis of his sample. He adds: "If additional analysis vindicates the initial positive result, I will argue that I have been the victim of poisoning."
Having finished third in last year's race, Schleck was 12th in the 2012 standings at the time of his removal, nine minutes behind leader Bradley Wiggins.
Despite its decision to remove Schleck, RadioShack-Nissan, which is currently leading the team standings in the 2012 Tour, says it is determined to maintain its representation in this year's event.
A statement on the team's official website read: "Our team attaches great value to transparency. After being informed by the UCI [the sport's governing body] about the presence of xipamide in the urine sample of Frank Schleck on July 14, the team has decided to immediately withdraw him from the Tour de France.
"On the subject of xipamide the team can declare the following: it is not a product that is present in any of the medicine that the team uses, and the reason for the presence of xipamide in the urine sample of Mr. Schleck is unclear to the team. However, the team is fully determined to collaborate with the anti-doping agencies in order to resolve the matter."
RadioShack Nissan was set up in 2010by seven-time Tour de France winner Lance Armstrong, who himself has recently been embroiled in drugs allegations.
The removal of Shleck follows the suspension of French rider Remy di Gregorio on 10 July, following allegations that he may have attempted to use banned substances.
Gregorio, who was in 35th place when he was withdrawn, was also questioned by police in relation to the charges. Jacques Dallest, a Marseille naturopath, has admitted to injecting ozone and glucose into Di Gregorio's bloodstream.
Di Gregorio has continued to insist he is innocent, saying "I have never doped".
Organisers of the Tour, which is about to enter a gruelling stage around the Pyrenees town of Pau, have yet to make an official statement regarding the drugs controversies.