A HALF-NAKED fan caused chaos at the Vuelta a Espana with several cyclists crashing during stage two.<br /><br />One rider was left enraged after claiming he collided with a "drunk fan" in the hills of Portugal, with the race not reaching Spain until stage four on Tuesday.<br /><br />Fans got carried away as they watched the peloton climb uphill with one fan sprinting wearing only his underwear.<br /><br />Riders were given a narrow passage to squeeze through with excited fans on either side of the road cheering them on.<br /><br />Seconds after the half-naked fan veered of course several riders fell.<br /><br />Trek rider Mathias Vacek, who finished second in stage one and just two seconds off winner Brandon McNulty, was one of them.<br /><br />He bemoaned his lack of luck on social media after crashing, claiming a drunk fan was to blame.<br /><br />Vacek said: "Not my luckiest day today after crashing because of a drunk Fan ♂️<br /><br />"But I managed to get safe to the finish with no serious injuries <br />Great job from the @lidltrek mates keeping everything under control "<br /><br />Unfortunately for Vacek, there were just over four kilometres left in the stage which meant he was unable to launch an attack in a bid to overhaul the two-second deficit he had to race leader McNulty.<br /><br />Instead, Wout van Aert took advantage of the chaos to claim the red jersey, and he now leads the race ahead of McNulty and Vacek, who make up the top three.<br /><br />Brit Joshua Tarling is down in sixth, 11 seconds off the leader while one of the favorites to win overall, Primoz Roglic, is eighth.