Michele Scarponi, the 2011 Giro d'Italia champion, has been killed after being hit by a van while training close to his home in Filottrano, Italy, his Astana team said on Saturday.
Scarponi, 37, left home early on Saturday morning for a training ride. The accident happened at a crossroads.
"This is a tragedy too big to be written," Astana said in a statement in English.
"We left a great champion and a special guy, always smiling in every situation, he was ... a landmark for everyone in the Astana Pro Team."
Scarponi, who completed the Tour of the Alps on Friday, after winning a stage and finishing fourth overall, is survived by his wife and two children.
He started his professional career in 2002 and his best results were in Italian races, winning three stages on the Giro before being handed the 2011 title after Alberto Contador was stripped of his victory because of a retroactive doping ban.
He also had good results in one-day races, finishing fourth on the Liege-Bastogne-Liege classic in 2003.
Scarponi was suspended for 18 months after being implicated in the Operation Puerto blood doping scandal in 2006.
After he returned from suspension, he won the Tirreno-Adriatico in 2009 and the Tour of Catalonia in 2011.
Tributes poured onto social media as riders remembered one of their friendliest colleagues.
Olympic champion Greg van Avermaet wrote: "We will miss this guy in the peleton, always with a smile."
Contador, Scarponi's team mate in 2005 and 2006, said: "Paralized and speechless ... great person and always with a contagious smile. Rest in peace my friend."
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