Mayo is a former Dauphine Libere winner

The mountain specialist tested positive for the banned blood-boosting drug erythropoietin (EPO) on 24 July, which was the Tour's final rest day.

Mayo, 29, is a team-mate of Britain's David Millar, an outspoken critic of cycling's drug culture since serving a two-year ban, also for using EPO.

This year's Tour was rocked by a series of drug-related revelations.

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In a statement, Mayo's employers said: "The Saunier Duval team were notified by the International Cycling Union (UCI) that Iban Mayo tested positive for EPO following a test on 24 July."

The statement added that they had decided to suspend him immediately and would sack him if the B sample also tested positive test.

In June, Mayo was reported to have tested positive for excessive testosterone after a stage win in the Giro d'Italia.

He was cleared by the UCI but president Pat McQuaid said the Spaniard had been singled out by testers as a potential future offender.

"People need to understand, the riders need to understand that that the UCI operates in a different way than in the past," said McQuaid.

"Thanks to the blood tests, we target riders - Iban Mayo was one of the UCI targets.

"The riders have to understand that we use intelligence to target some of them."

Meanwhile, Germany's Patrik Sinkewitz, who testing positive for high levels of testosterone in a pre-Tour test, has decided not to have his B sample tested, and been sacked by his T-Mobile team

Although the test was carried out in early June, the positive result was not made public until 18 July, three days after he was forced to pull out of the Tour after colliding with a spectator.

Sinkewitz said he had procured Testogel, a substance that he said is used on the skin to balance out a testosterone deficit.