Italian rider Ricardo Ricco of Saunier Duval has tested positive for blood booster erythropoietin (EPO), the French national anti-doping agency (AFLD) confirmed on Thursday.
The 24-year-old Ricco, winner of two mountain stages, provided a urine sample which contained the banned subtance CERA (Continuous Erythropietin Receptor Activator), French sports daily L'Equipe reported earlier on their website.
His Saunier-Duval team have confirmed that they are withdrawing from the Tour.
Ricco was sitting ninth overall while teammate Juan Jose Cobo was in eighth position.
Veteran team member Leonardo Piepoli won Monday's tenth stage.
Ricco was questioned by gendarmes before the start of Thursday's 12th stage between Lavlanet and Narbonne. He was then driven away by them in a Saunier Duval team car.
Ricco was one of the riders particularly targeted by the AFLD during the race and had been tested at least four times, L'Equipe reported.
All tests on the Tour are being carried out by AFLD because the race is being held under the auspices of the French federation.
That decision came in the wake of an ongoing feud between the International Cycling Union (UCI) and the company which runs the Tour, ASO (Amaury Sports Organisation).
The Italian won stages six and nine and was 2min 29sec behind Australian race leader Cadel Evans.
He becomes the third rider to fail a drugs test in this year's race after Spanish riders Moises Duenas of Barloworld and Manuel Beltran of Liquigas also tested positive for EPO.
