Oyarzun had failed a pre-competition test before last year’s Pan American Games in Toronto, with the Chilean Olympic Committee having announced his failure.

The Chilean cyclist was found to have tested positive for FG4592, a compound known informally as "oxygen in a pill".

“The Union Cycliste Internationale (UCI) announces that the UCI Anti-Doping Tribunal has rendered its decision in the case involving Carlos Oyarzun,” a UCI statement read.

“The Anti-Doping Tribunal found the rider guilty of an anti-doping rule violation and imposed a four-year period of ineligibility on the rider.

“In accordance with the Procedural Rules of the Anti-Doping Tribunal, the reasoned decision will be published on the UCI website in due course.”

Oyarzun, who won time trial bronze at the Guadalajara 2011 Pan American Games, was one of 21 positive tests recorded at Toronto 2015.

Colombia’s Maria Luisa Calle was the only other cyclist to be caught at the Games, with the 47-year-old having tested positive for GHRP2.

Calle, who controversially won a bronze medal in the Olympic points race at Athens 2004 only to be stripped of it before it was returned after the test was found to be faulty, was handed a four-year ban earlier this year.

Last year's total of 21 marked a significant increase on the four cases registered at each of the last two Games, Rio 2007 and Guadalajara 2011, although some have said the Pan American Sports Organization (PASO) deserve praise for catching so many.