Franck Schleck is to leave the Tour de France after the International Cycling Union (ICU) revealed he had tested positive for a banned substance.
Schleck, from Luxembourg, finished third in the iconic race last year but his Radioshack team have said he will take no further part in the Tour after he tested positive for the diuretic Xipamide.
A statement from the sport's governing body said a sample collected from Schleck on July 14 had failed their screening process.
"Earlier today the UCI advised the Luxembourger rider Frank Schleck of an adverse analytical finding (presence of the diuretic Xipamide...) in the urine sample collected from him at an in competition test," the UCI said.
"The UCI Anti-Doping Rules do not provide for a provisional suspension given the nature of the substance, which is a specified substance.
"However, the UCI is confident that his team will take the necessary steps to enable the Tour de France to continue in serenity and to ensure that their rider has the opportunity to properly prepare his defense in particular within the legal time line, which allows four days for him to have his B sample analyzed."
According to the World Anti Doping Agency, an offense involving a specified substance allows a tribunal more flexibility, and recognizes it is possible for such a substance to enter an athlete's body inadvertently.
"There is a greater likelihood that these substances could be susceptible to a credible non-doping explanation," their website explains.
Soon after the ICU's statement, Radioshack responded with one of their own stating Schleck would take no further part in this year's Tour.
Schleck is the brother of Andy, who was belatedly awarded with the 2010 Tour de France title after Alberto Contador's original victory was wiped out for doping offences.