Belgian cyclist Wouter Weylandt, 26, died in a crash during a downhill portion of the Giro d'Italia event, according to SteepHill.tv, a cycling site that was broadcasting the competition.
Weylandt's death marks the first time in 16 years a cyclist has died during a major event. Italian rider Fabio Casartelli died in the 1995 Tour de France. Three other cyclists have died during the Giro event since it began.
When he crash, Weylandt was going downhill, just about 12 miles from the finish, according to SteepHill.tv, during the third stage of the 21-stage, 107-mile event. Weylandt won the same stage in last year's race.
After Monday's crash, announcers said Weylandt was laying unconscious on the pavement. He was unresponsive on the course, even after a medical team cut his helmet to try to perform CPR, according to cycling site VeloNation.
The site said Weylandt was flown to a nearby hospital, but doctors couldn't do anything. The BBC reported dcotors tried for 40 minutes to revive him.
"Things like this shouldn't happen. Absolutely sick to the stomach," British cyclist Mark Cavendish wrote on Twitter, as he immediately reacted to the news. "My thoughts are with his family. RIP Wouter Weylandt."
Weylandt joined the Leopard Trek team earlier this year.
"The team is left in a state of shock and sadness and we send all our thoughts and deepest condolences to the family and friends of Wouter," according to a statement from his team published by VeloNation.
"This is a difficult day for cycling and for our team, and we should all seek support and strength in the people close to us," it concluded.
"We lost a great team mate and a true friend today," the team 's Twitter page said. "Our thoughts are with Wouter's family and friends."