Image 1 of 5 Alberto Contador put more time into his rivals on Thursday. (Image credit: Tim de Waele/TDWSport.com) Image 2 of 5 Giro d'Italia race leader Alberto Contador (Tinkoff-Saxo) Image 3 of 5 Alberto Contador with his brother Fran before the stage start (Image credit: Bettini Photo) Image 4 of 5 Alberto Contador on the stage 18 podium. (Image credit: Tim de Waele/TDWSport.com) Image 5 of 5 Alberto Contador drops Steven Kruijswijk during stage 18 of the Giro d'Italia. (Image credit: Courtesy of Polartec-Kometa)

Alberto Contador has called suspicions that riders are using secret motors in their bikes "a joke ... something from science fiction", but the UCI is taking every step to ensure that so-called mechanical doping is not taking place at the Giro d'Italia.

It's a rumour that first began when Fabian Cancellara rode away from Tom Boonen on the Kapelmuur in the Tour of Flanders in 2010, and although no evidence was found even after the UCI instituted bike checks, the issue continues to simmer.

In this video, the bike of race leader Contador is put through a series of checks by the officials, who even pull out the bottom bracket to find - nothing.

Should the UCI find evidence of motors, it now has recourse with rules introduced this year to punish riders with a six month ban for rider and team, and a 1 million Swiss Franc fine.

Do you think riders are using motors? Join the discussion on the Cyclingnews Forum here.

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