PARIS -- Three-time Tour de France champion Alberto Contador tested positive for a banned drug while winning this year's race and has been suspended by cycling's governing body, dealing a potentially crushing blow to his sport's efforts to shake off its doping-soiled past.
Contador blamed contaminated food for the test result.
A World Anti-Doping Agency-accredited lab in Cologne, Germany, found a "very small concentration" of the muscle-building and fat-burning drug clenbuterol in the Spanish rider's sample on July 21 at the Tour, according to a statement from the UCI.
But the amount was "400 time(s) less than what the antidoping laboratories accredited by WADA must be able to detect," the cycling organization said.
Both Contador's A and B samples tested positive and the cyclist has been "formally and provisionally suspended," the UCI said.
With seven-time Tour champion Lance Armstrong now back in retirement, Contador is cycling's biggest star, so it could be devastating for the sport if he is proved to have cheated.
Having invested millions of dollars in recent years in what is widely regarded as the one of the most stringent anti-doping regimes anywhere, cycling authorities hoped to be turning the corner on widespread doping by riders that had long made a mockery of the sport and repeatedly sullied the Tour, its showpiece race. Although just 27, Contador is already the greatest rider of his generation. His victories at the Tour starting in 2007 and at other major races were seen as a possible break from cycling's dirty past.
The UCI's statement gave no indication of whether Contador will be stripped of his latest Tour title or be banned.
"The UCI continues working with the scientific support of WADA to analyze all the elements that are relevant to the case. This further investigation may take some more time," the statement said.
It said the UCI would have no further immediate comment. Neither UCI president Pat McQuaid nor Tour de France director Christian Prudhomme picked up calls early Thursday to their mobile phones.
"This is serious and this case needs to be clarified," Pierre Bordry, the outgoing head of France's anti-doping agency, told RTL radio. "Clenbuterol is a forbidden substance, whatever the amount which is detected. If they really found it, it's forbidden."
Bordry announced his resignation from the AFLD last week. He said he was made aware of Contador's positive test on Wednesday night.
Jacinto Vidarte, Contador's publicist, released a statement saying the cyclist insists food contamination is 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 was scheduled to hold a news conference Thursday in Pinto, his childhood home in Spain.
WADA director general David Howman told The Associated Press that testing positive for even the most minute amounts of clenbuterol could be enough to sanction an athlete, although he declined to discuss the specifics of Contador's case.
"The issue is the lab has detected this. They have the responsibility for pursuing. There is no such thing as a limit where you don't have to prosecute cases. This is not a substance that has a threshold," said Howman, reached by telephone as he was changing planes in Dubai on his way to the Commonwealth Games in India.
"Once the lab records an adverse finding, it's an adverse finding and it has to be followed up."
"Clenbuterol is a substance that has been used for over 20 to 30 years," he added. "It is not anything new. Nobody has ever suggested it is something you can take inadvertently."
Contador was first made aware of the positive test on Aug. 24, according to Vidarte's statement.
Douwe de Boer, a Dutch anti-doping expert hired by Contador to study his test, said the rider told him that smaller traces of clenbuterol were also found in his urine in the two days after the positive result but were so minute that the UCI classed them as negative.
All of Contador's tests before July 21 were negative, De Boer said. The July 21 test was conducted on a rest day at the Tour, when the race was near France's border with Spain. De Boer said friends from Spain visited Contador and brought meat with them -- he believes it was beef -- "to celebrate their meeting."
"My conclusion is that it is very likely that this extra-low concentration (of clenbuterol) entered his body without him knowing it and one of the scenarios is contaminated meat," de Boer said in a telephone interview. He said the UCI's "lack of speed" in deciding whether to sanction Contador suggests that the cycling body is "seriously" considering the argument that contaminated food was to blame.
Contador beat Andy Schlock of Luxembourg by 39 seconds in winning his third Tour in four years.
Contador is a lithe but powerful rider who likes to use explosive bursts of speed up sharp mountain climbs to shake off rivals. Having won all three Grand Tours of France, Italy and Spain, something Armstrong never achieved, he appeared destined to become one of cycling's all-time greats.
If Tour officials strip Contador of his title, he would be just the second cyclist so punished. The first was American Floyd Landis, who was stripped of his 2006 Tour title after a positive test. For years, Landis denied doping but admitted this spring that he used performance-enhancing drugs. In doing so, he accused Armstrong and others of systematic drug use.
Federal agents in the United States probing suspected doping in US pro-cycling have been trying to corroborate Landis' claims. Armstrong insists he rode clean and says Landis has no credibility. On Wednesday, a US federal grand jury convened for the investigation heard testimony from exercise physiologist Allen Lim, who has worked with both Landis and Armstrong.
Armstrong, who retired in 2005 but came back three years later, and Contador had a fractious relationship when they rode together on the Astana team at the 2009 Tour. Contador won that year, while Armstrong placed third. Armstrong said then that Contador has the potential to become a five-time Tour winner. Armstrong is now back in retirement after riding poorly at this year's Tour. This August, Contador departed Astana and signed for the next two years with the Saxo Bank-SunGard team.
A spokesman for Saxo Bank had no comment.
"We are waiting for information to find out what is true and false in this matter," Kasper Elbjorn told The Associated Press.
Astana team director Yvon Sanquer was not immediately available for comment.
Elbjorn said the information should be provided by team manager Bjarne Riis. Riis didn't answer his phone Thursday.
Riis admitted in 2007 he had used the performance-enhancing drug EPO from 1993-1998, including when he won the Tour de France in 1996.
At Astana, Contador rode this year with Alexandre Vinokourov, who served a two-year ban for blood doping during the 2007 Tour. In France, prosecutors have also been investigating syringes and transfusion equipment found by police in a medical waste container traced to Astana's 2009 Tour team. In 2008, Contador was unable to defend his Tour crown because Astana was banned from the race following Vinokourov's blood-doping violation the year before.
Clenbuterol is not a steroid but does have anabolic properties that build muscle while burning fat. It is commonly given to horses to treat breathing problems. In medicine, it is used to treat asthma. In similar ways to stimulant drugs such as amphetamine or ephedrine, it can increase the heart rate and body temperature. Athletes and body builders are thought to use it in combination with other performance-enhancers such as growth hormone and steroids to build and define muscles. It is listed by WADA as an anabolic agent that is prohibited for use by athletes at all times, both in and out of competition.
American swimmer Jessica Hardy tested positive for clenbuterol at the U.S. trials in July 2008. She served a one-year suspension that ended last summer. The Court of Arbitration for Sport accepted her explanation that she had unknowingly taken it in a contaminated food supplement.
A number of athletes have been banned in recent months after using the banned drug, including Polish canoeist Adam Seroczynski, British hurdler Callum Priestley and Chinese Olympic judo champion Tong Wen.
Two cyclists also have been accused of using the drug and suspended. In May, the International Cycling Union suspended Italian cyclist Alessandro Colo after he tested positive for clenbuterol during the Tour of Mexico in April. And Chinese rider Li Fuyu, a member of Armstrong's Team RadioShack, was suspended in April after testing positive during a Belgian race.
Former New York Mets clubhouse employee Kirk Radomski admitted to distributing clenbuterol to dozens of current and former Major League Baseball players and associates in his plea deal.
Like cancer-survivor Armstrong, Contador has rebounded from a brush with death. After falling hard in a race in 2004 and persistently feeling unwell, Contador was diagnosed with a brain problem known as cavernoma, which can cause blood leakages, seizures and strokes.
He only returned to cycling the following year, and carries a large scar running down the side of his head from surgery to correct the problem. Contador has said that while recovering, he drew hope from Armstrong's book recounting his comeback from cancer.