Alberto Contador , a three-time winner of the Tour de France , tested positive for a banned substance on the final rest day of the Tour in July, according to a statement sent Wednesday by his spokesman, Jacinto Vidarte. 
 
 Contador, a Spaniard formerly on the Astana team, could lose the title he won this year and face a two-year suspension. 
 
 He learned about the positive test for the banned drug clenbuterol, a weight-loss and muscle-building drug, on Aug. 24, nearly a month after winning the Tour, the statement said. He had tested positive for the substance on July 21, one day before the race’s decisive mountain stage. 
 
 Contador, who has signed to ride for the Saxo Bank team next year, said he ingested the drug accidentally. 
 
 “The experts consulted so far have agreed also that this is a food-contamination case, especially considering the number of tests passed by Alberto Contador during the Tour de France,” his statement said. 
 
 Pat McQuaid, president of the International Cycling Union, did not immediately return phone calls, but the cycling union released a statement saying that Contador had been provisionally suspended and that his urine sample had a “very small concentration” of the banned drug. 
 
 “This case required further scientific investigation before any conclusion could be drawn,” the statement said. 
 
 Contador, 27, is widely known as the best stage racer in the world, having won each of cycling’s top three races: the Tour de France, the Giro d’Italia and the Vuelta a España. Despite a very public and testy battle with Lance Armstrong, his teammate at the time, for leadership of their Astana team, he won his second Tour in 2009. 
 
 This year, even after Armstrong took nearly the entire Astana team with him to his Team RadioShack, Contador won the Tour again, beating Andy Schleck by 39 seconds and retaining his spot as the sport’s top rider. 
 
 Contador, a national hero in his native Spain, is scheduled to speak about his positive test Thursday at a news conference in Pinto, his hometown. Though he never failed a drug test before, Contador in 2006 was initially implicated in a large-scale blood-doping ring in Spain. Later, the International Cycling Union cleared him of any wrongdoing. 
 
 At last year’s Tour, Contador reportedly set a speed record during one climb, prompting questions — including ones from the three-time winner Greg LeMond — about whether he was clean. In response, Contador said he had never taken performance-enhancing drugs and was against the doping that had weakened his sport’s credibility. 
 
 One of the biggest doping controversies hit the sport in 2006, when Floyd Landis won the Tour, then was stripped of the title after testing positive for synthetic testosterone. Landis had insisted that he had never used performance-enhancing drugs, but this spring he admitted using them. 
 
 If Contador is stripped of his Tour title, he will become the second rider to lose the title because of doping. And it looks as if he will have an uphill battle to retain that title. 
 
 The presence of the drug in an athlete’s system means that the athlete is disqualified from the day of the positive test forward, according to World Anti-Doping Agency rules. But if it is proven that the ingestion of the drug was unintentional and that the athlete was not at fault, that ban could be reduced to zero in rare cases, antidoping experts say. 
 
 Traces of clenbuterol have been found in nutritional supplements. The swimmer Jessica Hardy missed the 2008 Olympics after testing positive for the drug; she said she had taken a contaminated supplement. An arbitration panel later ruled that her claim was true and reduced her two-year ban to one year. ||||| Three-time Tour de France winner Alberto Contador tested positive for a banned steroid during this year's race, according to a statement released by his spokesman Wednesday. 
 
 Jacinto Vidarte, Contador's publicist, said the substance, identified as clenbuterol, was found in a test taken on July 21. Contador has blamed food contamination as the only possible explanation. 
 
 "The experts consulted so far have agreed also that this is a food contamination case, especially considering the number of tests passed by Alberto Contador during the Tour de France," Vidarte said in the release, "making it possible to define precisely both the time the emergence of the substance as the tiny amount detected, ruling out any other source or intentionality." 
 
 Contador will hold a news conference on Thursday in Pinto, Spain. 
 
 Contador was first made aware of the positive test on Aug. 24, according to statement, and has provided his explanation to the proper authorities.
– Tour de France winner Alberto Contador has tested positive for a banned substance and may be stripped of his title. The cyclist tested positive for "a tiny amount" of the banned drug clenbuterol on the final day of the race, according to his spokesman, who blames the result on food contamination. The Spaniard, a three-time Tour de France winner, could face a two-year suspension from cycling, AP reports. "The experts consulted so far have agreed also that this is a food-contamination case, especially considering the number of tests passed by Alberto Contador," the spokesman said. The International Cycling Union has provisionally suspended Contador, and plans an investigation, the New York Times reports. The cyclist, who has never failed a drug test before, is scheduled to hold a press conference today in his hometown in Spain.