Paris - Eight cyclists returned positive doping tests during August's Tour of Colombia, seven used a variant of the blood booster EPO known as CERA, the International Cycling Union said on Wednesday.
A UCI press release revealed the doping controls had been carried out on the basis of intelligence that had been uncovered.
CERA is effective for up to a month and does not show up in urine tests, but it can be detected by blood tests for 5-6 days after injection.
Luis Alberto Largo, Jonathan Paredes, Edward Diaz, Fabio Montenegro, Luis Camargo, Fabian Lopez and Oscar Soliz all tested positive for CERA on August 1 or 2 while Juan Carlos Cadena returned a positive testosterone sample August 11.
Soliz, who is Bolivian, was the best of the eight, finishing eighth in the general classification. The other seven are all Colombian.
All eight have been provisionally suspended pending a ruling and all may appeal for their 'B' samples to be tested.
The most recent positive test for CERA resulted in cyclist Joao Marcelo Pereira Gaspar being hit with a four-year ban.