Mayo is a former Dauphine Libere winner
Spanish cyclist Iban Mayo's 'B' sample for his positive drugs test in the 2007 Tour de France will be re-analysed after returning an inconclusive result.
On Monday Mayo, 30, was told the 'B' analysis from his positive test for erythropoietin (EPO) was negative.
But the International Cycling Union (UCI) says Mayo is not yet clear.
"The Paris lab was closed when the sample was to be tested," said UCI president Pat McQuaid. "It was done in Ghent - the result was inconclusive."
The mountain specialist, who finished the Tour in 16th place overall, was immediately suspended while his Saunier Duval team awaited the results of his B sample.
Mayo has said he is considering taking legal action against the UCI over the way he has been treated.
"It was a very bad experience because I didn't understand what was happening but everything has turned out as I expected," he told Spanish newspaper Marca.
"It doesn't seem logical nor credible," he said. "I've spent many years cycling and I can't chuck it all in but sometimes you feel like it because there are so many injustices.
"The fans who like cycling don't want to see this sort of thing. Cycling is a spectacle that involves sacrifice if not you don't get the results."
Mayo, who joined Saunier Duval from the Euskaltel Euskadi team last October, has frequently been tipped to shine in the Tour de France but has failed to live up to expectations.
He finished sixth in the Tour in 2003 and won the Dauphine Libere race in 2004.