"The team management and the rider were both totally surprised by this physiological result," Phonak added.

"The rider will ask in the upcoming days for the counter analysis to prove either that this result has come from a natural process or that this is the result of a mistake," the statement read.

Landis pulled out of races in the last two days without giving any explanation and organisers of those events were unable to contact him.

Dutch news agency ANP quoted his team mate Koos Moerenhout as saying that Landis had pain from a hip problem and had gone gone to see his doctor in Germany.

The UCI announced on Wednesday a rider had tested positive during this year's race. The ruling body did not name the rider or give further details.

DOPING SCANDAL

This year's Tour was hit by a doping scandal on the eve of the opening prologue.

Giro d'Italia winner Ivan Basso of Italy and Germany's 1997 Tour champion Jan Ullrich were forced to pull out and were suspended after being implicated in a doping investigation in Spain. The pair denied any wrong-doing.

Ullrich was later sacked by his T-Mobile sponsor while team mate Oscar Sevilla and manager Rudy Pevenage were suspended.

The Astana-Wuerth team had to withdraw as five of their riders were on a list of nine Tour competitors provided by Spanish police in the biggest doping scandal since the Festina affair which rocked the 1998 race.

The investigation came to light in May when the Spanish Civil Guard raided addresses in Madrid and Zaragoza and found large quantities of anabolic steroids, equipment used for blood transfusions and more than 100 bags of frozen blood.

A notoriously tough sport, cycling has been plagued by doping for years.

Landis's win had been welcomed by observers, who said it lifted some of the gloom hanging over the event after its traumatic start.

Asked if he had a message to deliver about doping after his victory, Landis had said: "In this sport, we proved that more than any sport we try to prevent doping and try to solve the problem.

However, he added: "Cycling has a reputation that doesn't seem to want to go away."