Chilean Jose Medina Andrade and Argentine Alfredo Lucero have returned positive doping tests from the Vuelta Ciclista de Chile, according to the International Cycling Union.
The pair join Marco Arriagada as having tested positive for stanozolol metabolites during the event won by Arriagada, "based on reports from the WADA accredited laboratory in Los Angeles in the urine samples collected from them at in-competition tests," it was announced via statement.
All three riders now "have the right to request and attend the analyses of their B samples."
Stanozolol is an anabolic steroid, infamously used by Canadian sprinter Ben Johnson when he was stripped of his gold medal in the Seoul Olympic Games 100m final.
News of Arriagada's positive first surfaced last month where he told emol.com: "I deny it emphatically,"
"I'm returning to Chile to perform all the tests to prove my innocence," he continued. "The Federation informed me and now we have to see with my lawyers."
Arriagada has dominated the Latin American calendar since the turn of the year, with wins in Argentina, Chile and the Dominican Republic. His Tour de San Luis victory was particularly noteworthy, as the 35-year-old saw off a field including the likes of José Serpa, Xavier Tondo and Ivan Basso to take overall honours.