Tour de France champion Alberto Contador has tested positive for a banned substance.

Contador, who this year added a third Tour title to his 2007 and 2009 successes, tested positive for clenbuterol on July 21.

The Spaniard’s spokesman Jacinto Vidarte said the 27-year-old was first told of the test by the UCI on August 24.

The UCI later confirmed that Contador had been provisionally suspended.

“It is a case of food contamination to which I was the victim,” Contador told a news conference.

“The UCI itself affirmed in front of me that it was a case of food contamination,” he added.

“This is a genuine mistake, it’s sad that a sport such as this … is involved in things like this.

“I think that this will be resolved in a clear way, with the truth up front. [The UCI] understands that is a special case, which has to be examined.”

A lab in Cologne, Germany, found a “very small concentration” of clenbuterol in Contador’s urine sample, the UCI said.

The amount was 50 pictograms – 400 times less than what anti-doping laboratories accredited by the World Anti-Doping Agency must be able to detect.

Vidarte added: “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.”

The UCI have not commented on whether Contador will be stripped of his latest Tour title or banned.

United States cyclist Floyd Landis was denied his 2006 crown for a positive drugs test. 

Clenbuterol is a stimulant that increases breathing capacity and improves the flow of oxygen in the bloodstream.

It can be prescribed to treat asthma but is also used to reduce body fat.

Meanwhile, the UCI have confirmed Vuelta a Espana runner-up Ezequiel Mosquera and Xacobeo-Galicia team mate David Garcia both failed drugs tests during the recent Grand Tour. 

Traces of Hydroxyethyl starch have been detected in urine samples taken from both riders on September 16, when Mark Cavendish won stage 18.