Paz Duque failed for the blood booster at the Milan round of the Red Hook Criterium on October 1, a statement from race organisers said.

He is now banned for life from the fixed-gear Red Hook series, as per the rules of the event.

The positive test is the first doping revelation for the series, which also features fixed-gear races in Brooklyn, London and Barcelona.

Red Hook was launched in 2008 and in 2013 became an international series.

"It’s unfortunate - we always wanted to believe that the Red Hook Crit represented a new way in cycling, but you can’t be naive," said David Trimble, the series’ founder, to VeloNews.

In recent years, the series began attracting riders with professional road racing credentials.

"When we started to get crossover from road racing we knew it was a risk," Trimble added.

Paz Duque competes for Paraguay’s Vivo Team Grupo Oresy road team, which is registered as an International Cycling Union (UCI) Continental team.

The Red Hook series sends doping samples to the World Anti-Doping Agency (WADA) accredited Sports Medicine Research and Testing Laboratory in Salt Lake City in the United States. 

Officials perform doping controls on the top three men and women, and also test random finishers.

Paz Duque, who finished 38th in Milan, was one of those chosen at random.

The series forbids athletes with any doping history from competing in any round of the Red Hook Criterium.

In previous years former ProTour riders Riccardo Ricco and Carlos Barredo have been prevented from participating after both men previously received sanctions for doping.

"Obviously this news sucks but it shows that we’re taking it seriously," Trimble added.

"If someone is thinking of doping and coming to the Red Hook Criterium, they’re going to be worried now."