The International Cycling Union, the UCI, has asked Spain's cycling federation to open disciplinary proceedings against Tour of Spain runner-up Ezequiel Mosquera who tested positive last year.
Mosquera tested positive for hydroxyethyl starch, a plasma substitute that can increase blood volume.
The UCI conducted further scientific investigations in collaboration with the World Anti-Doping Agency accredited laboratory of Cologne in order to ascertain the origin of the results.
Mosquera, who could face a two-year ban, told a news conference last year his conscience was clear.