Three-time Tour de France winner Alberto Contador denies that his positive test for a banned drug stems from blood doping rather than contaminated steak, his spokesman said earlier today.

The French sports daily L'Equipe reported Friday that the German lab that found a tiny amount of the banned drug clenbuterol in Contador's urine sample also found plastic residues of the kind that might turn up after a transfusion of blood from a plastic bag.

German national television station ARD also reported that plastic traces were detected.

Contador spokesman Jacinto Vidarte told The Associated Press the Spanish rider "categorically denies having a blood transfusion."

"There is nothing to that," he said. "It is a science fiction story."

Vidarte said no one at the International Cycling Union, which announced Contador's positive test Thursday and his temporary suspension, has told Contador that plastic residues were found.

Vidarte said the World Anti-Doping Agency has not validated a method for detecting plastic from blood transfusion bags.

WADA director general David Howman, however, told the AP that a method was "fully validated and has been used in the food industry for years."

"Its use for anti-doping purposes is partially validated and evidence from it, among others, can be used before tribunals," Howman said.

The detection method has been developed by the WADA-accredited lab in Barcelona.

Douwe de Boer, a Dutch anti-doping expert hired by Contador to analyze his positive test result, has seen the report compiled by the German lab in Cologne and saw no mention of plastic residues, Vidarte said.

Contador on Thursday denied using clenbuterol and said the trace elements found in his urine came from beef he ate during this year's Tour -- once on July 20 and again on a rest day July 21, the day the drug was found in his urine.

If Contador is found guilty of doping, he faces the loss of his Tour de France title and a possible two-year ban.

Professor Michel Audran, a leading expert in blood doping, told the AP that the Barcelona lab published a study last year showing that the amount of plastic traces in people receiving a blood transfusion is twice that as those found in the general population's samples.

"If we find a high amount of plastic traces in Contador's samples, the blood transfusion can't be ruled out," he said.

UCI president Pat McQuaid refused to comment on specifics of the Contador case Friday.

"It's an independent process," he told the AP in Australia, where he is attending the world road racing championships. "The UCI are working closely with WADA and we wait until we get to the process."

Contador's former team, Astana, issued a statement saying it supports the UCI's decision to provisionally suspend the rider and is "now expecting further explanations from Alberto Contador."