Alexandr Kolobnev of Russia became the first cyclist at this year's Tour de France to fail a doping test, the International Cycling Union said Monday.
Kolobnev was in 69th place heading into Tuesday's 10th stage, but his Katusha team issued a statement saying he is out of the Tour after deciding to "suspend himself according to UCI rules."
Katusha sports director Dimitry Konyshev had earlier told The Associated Press that "it's impossible for him to continue the race with this problem."
The UCI said a urine sample collected from Kolobnev last Wednesday tested positive for a substance called Hydrochlorothiazide, a diuretic that can also be used as a masking agent hiding the presence of other drugs. The samples were analysed at the Chatenay-Malabry laboratory, which is accredited by the World Anti-Doping Agency. It came on the Tour's fifth stage — a flat sprint from Carhaix to Cap Frehel.
Tour organizers and French Anti-Doping Agency president Bruno Genevois were not immediately available for comment.
Katusha sports director Bart Leysen said Kolobnev met team management then left the hotel with police officers to be questioned at the police station, adding that they "just want to check some things with him, papers, and normally they will bring him back later."
Asked if Kolobnev will be sacked from the team, Leysen replied: "Our riders all sign an internal document saying that in case of a positive test they are fired."
Kolobnev has four days to request an analysis of his "B" sample.
"If the 'B' sample also tests positive, he will be fired and will have to pay five times his salary as a fine," the Katusha statement read.
The UCI can't provisionally ban Kolobnev because Hydrochlorothiazide is classified as a specified substance, which WADA defines as one that is "more susceptible to a credible, non-doping explanation." Its punishment for such a positive test ranges from a warning to a two-year ban.
The 30-year-old Kolobnev finished 65th in last year's Tour. The former Russian champion had previously ridden in other races for Domina Vacanze, Rabobank, Team CSC and Saxo Bank.
His career highlights include finishing runner-up at the 2010 Liege-Bastogne-Liege and a stage victory at the 2007 Paris-Nice.
Cycling's showcase race has been devastated by doping scandals over the years. Tougher new measures seemed to have produced fewer doping cases until defending champion Alberto Contador tested positive for the banned anabolic agent clenbuterol in last year's race.