ZURICH (AFP) - America's Olympic time-trial champion Tyler Hamilton has tested positive for blood doping in a second sample from the Tour of Spain, his Phonak team said.
However, the American rider has been cleared of committing a doping offence at the Olympic Games after the International Olympic Committee (IOC) admitted that the B sample on that test had proved inconclusive.
"The laboratory analysis of the B sample was considered as non-conclusive because of a lack of enough intact red blood cells," said an IOC statement late Thursday.
"The disciplinary procedure has had to be stopped and Tyler Hamilton has been informed that the IOC would not be pursuing sanctions regarding this matter."
The 33-year-old faces a possible two year ban after testing positive in the first sample for an allegedly illicit blood transfusion following his win on the Tour of Spain's eighth stage time trial earlier in September.
He pulled out of the Tour six days later apparently due to stomach problems.
But Phonak challenged the testing method, saying it was based on "probability and interpretation measurements" and "uncertainties will remain".
"Because neither UCI nor IOC have so far disclosed data and because legal procedures may last for a long time without a clear outcome, the team management has decided to establish a scientific board in order to achieve clarity as to the medical method and reliability of these new blood testing tools," it added.
Hamilton will remain suspended from the team while the probe is carried out, Phonak said.
"The team's goal is - and this is in the exact interest of Tyler Hamilton - that we have clarity at the end," a statement issued by the Swiss team said.
Earlier Thursday, Hamilton insisted he was innocent of blood doping at the Olympics, and had issued a broader denial earlier this week.
"I guarantee that I represented the United States of America as an honest, clean and proud athlete," he said.
"As the Olympic Committee did not promptly inform me of the alleged anti-doping violation until one month after the event on August 18, 2004, it was not possible to defend myself before."
"Regardless of this I will prove my innocence."
Blood doping is a means of enhancing an athlete's endurance by increasing the amount of oxygen-carrying red cells in the blood stream, using his own blood or a donor of the same group.
The method is believed to have entered sport in the 1970s but was not made illegal until 1986. It was made redundant in the late 1980s with the arrival of the synthetic version of the blood-boosting hormone erythropoietin (EPO).
But the fact that EPO has become detectable since 2000 has given rise to speculation that blood doping has returned.