Cycling:The Tour de France, which began with such high hopes when millions turned out to cheer its grand depart in the south of England two-and-a-half weeks ago, was in disarray last night after an announcement that the pre-race favourite, Alexandr Vinokourov of Kazakhstan, had tested positive for blood doping. He and his eight team-mates were immediately withdrawn from the race.

A sample taken from Vinokourov after Saturday's stage had shown traces of another person's blood of the same type. "Homologous blood doping" has been used in cycling and other sports to raise the count of red cells, thereby increasing resistance to fatigue.

Vinokourov's sample was taken as a matter of routine after he had won Saturday's 35-mile time trial in Albi, southwest France, by a margin that astonished those who had seen him suffering in the preceding days as a result of a bad crash earlier in the race. His knees had been heavily stitched by doctors while the Kazakh's legs were tucked in the riding position, so that he would be able to continue pedalling through the remainder of the 2,230-mile, 21-day event.

Still bandaged, he repeated the performance on Monday. Twenty-four hours after indicating what appeared to be terminal distress to TV cameras covering a mountainous stage in the Pyrenees, he soared away from the remainder of the 160-strong field up a series of lung-bursting climbs to win another stage.

His earlier problems - which included a second crash - had dropped him to 23rd place in the overall classification, almost half an hour behind the current leader, but the two stage wins appeared to be an act of pure defiance, earning a powerful accolade from L'Equipe, with a front-page headline that read "Le courage de Vino".

Vinokourov (33), fell under suspicion before the start of the race when he admitted to working with Michele Ferrari, a controversial Italian doctor closely associated with Lance Armstrong's record run of seven consecutive victories in the tour between 1999-2005. According to Vinokourov, Ferrari was merely his physical trainer. "He has never given me medicines," he said.

In the stage-winner's press conference on Monday, Vinokourov attempted to disperse the gathering rumours: "If I can help to solve the tour's problems, I'm ready."