Riccardo Ricco of Italy, right, is led away by French gendarmes prior to the start of the 12th stage of the Tour de France today. Ricco is the third cyclist who tested positive for the use of EPO in this Tour de France. Associated Press Photo.

LAVELANET, France — The Saunier-Duval team withdrew from the Tour de France and suspended all of its activities today after rider Riccardo Ricco became the third rider to test positive for the banned blood-booster EPO at this year’s race.

Ricco, a 24-year-old Italian who won two Tour stages this year, tested positive for the performance enhancer after the fourth stage, a time trial in the western town of Cholet.

Pierre Bordry, the head of the French anti-doping agency, announced the result, leading to the team’s withdrawal shortly before the start of the 12th stage — a 104.7-mile run from Lavelanet to Narbonne. Saunier-Duval is the first team to withdraw from this year’s Tour.

“It’s a team decision not to start the race,” Saunier-Duval sporting director Matxin Fernandez said. “He’s our leader; we can’t act as if nothing happened.

The Tour continues to struggle to eradicate doping after last year’s scandal-plagued event in which two teams withdrew and race leader Michael Rasmussen was kicked out just days before the end for lying about his whereabouts to avoid pre-Tour testing.

Cofidis dropped out after Cristian Moreni of Italy tested positive for testosterone, and pre-race favorite Alexandre Vinokourov’s Kazakh-owned Astana team was kicked out by race organizer ASO after he tested positive for blood doping.

In an attempt to salvage cycling’s showcase event, race organizers had pledged a tougher approach to combatting drug cheats at this year’s Tour. Eight specially trained chaperones shadow riders after each stage, even climbing onto team buses, to ensure cyclists go to post-stage anti-doping checks.

As part of the clampdown, the French anti-doping agency tested riders before the race and found that some 20 had abnormal levels of hematocrit without exceeding the limit. High levels of hematocrit are indicators of EPO use but do not confirm it.

Ricco was taken off the Saunier-Duval team bus by police ahead of the stage and booed by spectators.

Ricco was the runner-up in the Giro d’Italia and is the biggest name among three cyclists involved in doping cases at this year’s Tour. He won the sixth and ninth stages and was ninth overall before the start of Thursday’s stage — 2 minutes, 29 seconds behind race leader Cadel Evans of Australia.

Spanish veteran Manuel Beltran — a former teammate of seven-time Tour champion Lance Armstrong — was sent home for testing positive for EPO after the first stage this year. Another Spaniard, Moises Duenas Nevado, was detained by police and expelled from the race on Wednesday after testing positive for EPO — like Ricco, after the fourth stage.

Ricco had come under suspicion about what he says is his naturally high hematocrit level — the volume of red blood cells.

Following his victory in the ninth stage, Ricco said he has had high hematocrit levels “ever since I was little,” adding “I hope soon that everybody will stop speaking about that.”

Reached by telephone, the Italian cycling federation said it was waiting for details of Ricco’s test before commenting.

Ricco’s popularity in Italy rocketed with his two Tour stage wins, even gaining front-page coverage in the football-focused Gazzetta dello Sport.

The rider has said his idol was Marco Pantani — the last Italian to win the Tour, in 1998. Pantani faced doping allegations throughout his career. He died of a cocaine overdose on Valentine’s Day in 2004.

The news on Ricco came as judicial officials continued to question Duenas Nevado. He was detained by police Wednesday in the southwestern town of Tarbes, at a hotel where his Barloworld team was staying. Police also searched his hotel room.

Gerard Aldige, the state prosecutor in Tarbes, told The Associated Press that police found “numerous small medical materials like syringes, needles, and medical drip bags which theoretically a cyclist should not have in his room.”

Aldige said Duenas Nevado faced preliminary criminal charges for “holding and using poisonous substances or plants” and “prohibited importing of merchandise.”

Other substances were also found, including capsules and gels, but that tests will be required to determine their composition, Aldige said. He said one medicine not authorized for sale in France was also found — though he did not elaborate.

Beltran, who rides for Liquigas and is a former teammate of seven-time Tour winner Lance Armstrong, was kicked out of the Tour on July 11 after he tested positive for EPO.

In addition to Beltran, Floyd Landis, Roberto Heras of Spain and Tyler Hamilton — all former Postal riders during Armstrong’s seven Tour wins from 1999-2005 — failed doping tests after quitting the Texan’s team.

Some riders expressed dismay at the latest revelation of doping on the Tour.

“It’s just amazing. It’s irresponsible,” British cyclist David Millar said. “This guy does not have any love or care for the sport.

“The unfortunate is that we are learning that things that look too good to be true are too good to be true,” Millar added.