The UCI has called on the Spanish Cycling Federation (RFEC) to open disciplinary proceedings against Vuelta a España runner-up Ezequiel Mosquera.
Mosquera tested positive for a banned masking agent, Hydroxyethyl Starch, also known as HES, during an in-competition test at the race on September 16.
He denied knowingly taking any banned substances, saying his “conscience is clear.”
The UCI has since conducted “further scientific investigations in collaboration with the WADA (World Anti Doping Agency) accredited laboratory of Cologne in order to ascertain the origin of these results.”
Cycling’s world ruling body added in a statement: “At the end of this enquiry entrusted to highly qualified experts, and considering all the information currently in its possession, the UCI has concluded that disciplinary proceedings should be opened against Ezequiel Mosquera.
“It is now the responsibility of RFEC to determine whether Ezequiel Mosquera has breached the UCI Anti-Doping Rules.”
The RFEC, which earlier this year cleared Tour de France champion Alberto Contador from any wrongdoing after his positive test for clenbuterol at last year’s race, now has to decide whether to suspend Mosquera.
HES, which is banned by the World Anti-Doping Agency, can theoretically enhance performance by its ability to increase the blood volume, allowing red blood cells to continue to deliver oxygen to the body.
It is also known to fluidify the blood, thus being able to mask the use of blood boosting substances such as EPO (erythropoietin) by reducing the hematocrit level.
The UCI has set a permitted threshold of 50 percent for hematocrit. Riders who are found to have readings of 50 or above are provisionally suspended, pending further investigation.