Frank Schleck has left the Tour de France after failing a doping test, his RadioShack-Nissan-Trek team have confirmed.
Schleck, who finished third in the 2011 Tour, tested positive for banned diuretic Xipamide on 14, cycling's world governing body, the Union Cycliste Internationale announced.
His team confirmed that Schleck would not start tomorrow's 16th stage.
Schleck was 12th overall, nine minutes and 45 seconds behind leader Bradley Wiggins (Team Sky), at the second rest day and has the right to attend the analysis of his B sample.
The Luxembourg rider is the older brother of Andy, who won the 2010 Tour after original champion Alberto Contador was stripped of his title for a doping offence.
Andy Schleck missed this year's Tour due to injury.
A statement from the team read: "Our team attaches great value to transparency. Because of this, we can announce the following as a response to the adverse analytical finding of xipamide in Frank Schleck's urine sample of 14 July during the Tour de France.
"After being informed by the UCI about the presence of xipamide in the urine sample of Frank Schleck on 14 July, the team has decided to immediately withdraw Frank Schleck from the Tour de France.
"Even though an abnormal A sample does not require these measures, Mr Schleck and the team believe this is the right thing to do, to ensure the Tour de France can go on in calm and that Frank Schleck can prepare his defense in accordance with the legal timing to do so.
"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. Therefore, the team is not able to explain the adverse findings at this point.
"However, the team is fully determined to collaborate with the anti-doping agencies in order to resolve the matter."
The positive test came after Saturday's Bastille Day stage to Cap d'Agde.
The news came on the Tour's second rest day.
On the Tour's first rest day, Cofidis rider Remy di Gregorio was detained by French police investigating an alleged doping ring.