Olympic time trial champion Tyler Hamilton has been cleared of any doping offence at the Athens Games by the International Olympic Committee (IOC).
Hamilton's future remains uncertain
The IOC said that the result of the American's B, or second, test was "non-conclusive" because the sample had been destroyed by being deep-frozen.
Earlier, Hamilton's Phonak team stated the B test on a blood sample he gave at the Tour of Spain had tested positive.
Phonak said they are to investigate the discrepancies between the tests.
Hamilton had been told he gave a positive A, or
first, test for a blood transfusion in Athens on 18 August.
He then failed another test, conducted by cycling's govening body the UCI, after winning a time trial in the Tour of Spain on 11 September.
BLOOD DOPING EXPLAINED
What is it?
The administration of red blood cells to increase the blood's oxygen-carrying capacity
Injecting someone else's red blood cells; removing own blood and returning it once body has compensated by making more blood
Why would athletes do it?
The better the oxygen-carrying capacity of the blood, the better an athlete's endurance
Side effects can include:
Blood clots, overload of circulatory system, kidney damage, transmission of infectious diseases
Chances of being caught:
A new test can only detect the practice if the blood comes from a donor
Hamilton is the first cyclist to be found to have tested positive for blood doping - when athletes inject blood from another person in order to increase red blood cells and improve stamina.
Phonak said: "The new method (of blood testing) is based on probability and interpretation measurements (so) uncertainty will remain in this examination."
If the B sample from Hamilton's Athens test had been positive, he would have almost certainly lost his gold medal.
Arnie Ljungqvist, head of the IOC's medical commission, said it had been a mistake to deep-freeze Hamilton's B
"The blood sample was unfortunately destroyed. It should not have been deep frozen (in the laboratory)."
Hamilton, 33, has maintained he is is "100%" innocent of the charges.
He could be banned for two years, effectively ending
his career, if the UCI finds him guilty of doping offences in the Tour of Spain.