Ricco becomes the third rider to test positive for EPO on the 2008 Tour after Spaniards Manuel Beltran and Moises Duenas Nevado.
"It's for the same product as the other two," AFLD president Pierre Bordry said.
Police came to the Saunier Duval team's bus in southwestern Lavelanet before the start of Thursday's 12th stage to Narbonne. Ricco then left in a team car escorted by police.
He was arrested three kilometres from the team bus by the police and taken for questioning to the gendarmerie in Foix, a source within organisers ASO said.
"It shows that the controls are really efficient and that it is harder to get away with it," Tour de France director Christian Prudhomme said.
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