The usual substances were involved, specifically, a class called CERA which is a blood booster similar to Erythropoietin (EPO), and anabolic steroids.
All were detected based on intelligence apparently provided to the world governing body and carried out by the Cycling Anti-Doping Foundation (CADF), an independent body charged with "defining and implementing the anti-doping strategy in cycling," according to a statement published on the UCI website.
The list of riders identified as taking CERA in blood samples collected on 1 and 2 August 2017 includes Luis Alberto Largo Quintero (COL), Jonathan Felipe Paredes Hernandez (COL), Edward Fabian Diaz Cardenas (COL), Fabio Nelson Montenegro Forero (COL), Luis Camargo Flechas (COL), Fabian Robinson Lopez Rivera (COL) and Oscar Soliz Vilcaa (BOL).
Another, Juan Carlos Cadena Sastoque (COL) was the sole rider identified as taking the steroid 19-noretiocholanolone and 19-norandrosterone in a urine sample provided on 11 August 2017.
All riders will have the opportunity to request and attend the analysis of the B sample and all have been provisionally suspended until the matter is resolved.