Two separate blood samples provided by Olympic gold medalist Tyler Hamilton have come back with different results -- one positive and the other negative -- his Swiss-based team said Thursday.
The Phonak team also repeated doubts over the validity of the testing method, claiming the American could be a victim of fuzzy science.
One of Hamilton's `B' samples confirms the finding of the `A' sample tested at the Spanish Vuelta on Sept. 11, which showed evidence of blood from another person, said Phonak in a statement.
But Hamilton's `B' sample from the Athens Olympics -- where he won the time trial gold -- was clean, Phonak said on its Web site.
The American's original sample tested positive in Athens on Aug. 19 for evidence of blood from another person.
The findings only emerged this week, raising fears that Hamilton could lose his medal.
Hamilton, 33, said Tuesday he was 100 percent innocent and denied ever receiving a transfusion -- which can boost an athlete's performance by increasing the amount of oxygen-transporting red blood cells in his system. He repeated the denials Thursday.
If Hamilton is ultimately found guilty, it would be the first case related to a blood transfusion.
Phonak has threatened to fire Hamilton if he can't prove his innocence, and on Wednesday said it suspended him from racing. However, he remains part of the team, Phonak said Thursday.
In another statement posted on Phonak's Web site, Hamilton said: "I am still a member of the Phonak Cycling Team and will continue to participate in the day-to-day decisions concerning our team."
Cycling's governing body, UCI, had informed cyclists at the start of the season that it planned to start using a new blood-screening machine in the tests that detects blood transfusions, human growth hormone and synthetic hemoglobin.
Until now, there has been no foolproof test for detecting blood transfusions.
Phonak said it plans to gather a scientific team to investigate the accuracy of the new blood tests.
"Since the new method is an effort based on probability and interpretation measurements, uncertainties will remain in this examination and procedure in any case," Phonak said..
Spaniard Javier Pascual Rodriguez beat Colombia's Ivan Parra at the finishing line to take the 18th stage of the Vuelta cycling tour Thursday, his fourth win of the 21-stage race.
Defending champion Roberto Heras finished the 197km ride to the western walled city of Avila back in the pack, one minute, 24 seconds behind Rodriguez, and retained the leader's yellow jersey.
Heras is 1:13 ahead of fellow Spaniard Santiago Perez and 2:15 ahead of Alejandro Valverde, also of Spain.
Pascual Rodriguez followed Parra in a breakaway from the main pack with some 30km to go in the stage. Parra looked as if he could win until the final meters when Rodriguez edged out ahead and crossed the line first by less than a second. Rodriguez's winning time was five hours, two minutes and 59 seconds.
Spain's Joan Horrach and Colombia's Hernan Buenahora finished third and fourth, respectively, both 19 seconds behind Rodriguez.
The race has two more mountain stages before Sunday's final time trial in Madrid.
On Friday, the riders face a 142km route from Avila to Collado Villalba, just outside Madrid, with six mountain ascents, including one top-category climb.