Cycling:Cycling's world governing body announced late lasty night that Russian rider Alexandr Kolobnev has failed a doping test during the Tour de France.
The UCI said 30-year-old Kolobnev had given a urine sample which contained the diuretic hydrochlorothiazide, a prohibited 'specified substance'.
The sample was taken last Wednesday and Kolobnev has the right to request results of his B sample.
However, the fact that he would no longer play a part on this year's Tour was later confirmed when his team, Katusha, announced that they had withdrawn him.
The governing body said in a statement: "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 defence in particular within the legal timeline, which allows four days for him to have his B sample analysed.
"Under the world anti-doping code and the UCI anti-doping rules, the UCI is unable to provide any additional information at this time."
Katusha sporting director Sergei Kunitchev said: "We have decided with the agreement of the rider that he will be no longer with us on the Tour."
The team added that if Kolobnev's B sample also tested positive, he would be sacked and have to pay "five times his salary" as a fine.
Kolobnev becomes the first cyclist to fail a doping test during this year's race.
With Monday a rest day, he stands 69th in the overall standings after nine stages, 22 minutes and 15 seconds behind leader Thomas Voeckler.
The Russian has had a largely low-profile career but he won a bronze medal in the 2008 Olympics in the road-race event, being promoted from fourth place after second-placed finisher Davide Rebellin failed a drugs test.
He has also won two World Championship silver medals in road-racing.
Meanwhile Team Radioshack's Tour de France challenge suffered a further blow when Ukrainian road captain Yaroslav Popovych withdrew before the start of the 10th stage.
"Yaroslav Popovych will not start stage 10 in the Tour de France," the American team said in a statement.
"Since Sunday, Popovych has had a fever. As the rest day didn't bring any amelioration, the team decided not to let him start in Aurillac."
Popovych is the third Radioshack rider to pull out after team leaders Janez Brajkovic and Chris Horner abandoned the race when they sustained injuries following crashes.
German Andreas Kloeden, eighth in the overall general classification, will start the 158-km stage that finishes in Carmaux despite suffering from back pains.