Belgian rider Michael Goolaerts died of cardiac arrest after collapsing while competing in the Paris-Roubaix race on Sunday.
Goolaerts' team said the 23-year-old died in a Lille hospital where he had been taken by helicopter from the one-day classic.
"It is with unimaginable sadness that we have to communicate the passing of our rider and friend Michael Goolaerts," his team, Veranda's Willems-Crelan, said in a statement.
The team said Goolaerts died "in the presence of his family members and loved ones, who we keep in our thoughts." It added that he "died of cardiac arrest, all medical assistance was to no avail."
Goolaerts had been airlifted to hospital after collapsing about 150 kilometers (93 miles) from the finish. No images of the incident itself were available but TV footage of the race showed Goolaerts lying unresponsive on the side of the road as the peloton passed him. He was then attended by a medical team and appeared to receive CPR.
Goolaerts rode in support of cyclo-cross world champion Wout van Aert of Belgium. His most significant result this season was 20th at Kuurne-Brussels-Kuurne.
Peter Sagan won the race ahead of Silvan Dillier of Switzerland.
Goolaerts' death came two years after Belgian cyclist Daan Myngheer died following a heart attack during the Criterium International race in Corsica.
Another Belgian cyclist, Antoine Demoitie, died the same year following a crash in the Gent-Wevelgem race.