Unfortunately, 22-year-old Belgian cyclist Michael Goolaerts fell victim to these incredibly hard circumstances during this afternoon's race.
The 23-year-old was unconscious and not breathing when he was treated by the race's medical team, then firemen and finally an emergency mobile medical outfit, the fire brigade said.
"It is with unimaginable sadness that we have to communicate the passing of our rider and friend Michael Goolaearts", a statement posted on the Verandas Willems-Crelan Twitter page said.
'He passed away on Sunday evening at 22.40 in Lille Hospital in the presence of his family members and loved ones, who we keep in our thoughts.
This is published unedited from the ANI feed.
British Team Sky rider Geraint Thomas was forced to abandon the race after crashing on the first section of cobbles.
It was a second prestigious "Monument" one-day classic success for Sagan, who won the Tour of Flanders in 2016 and has three consecutive world titles. The race was also marred by several crashes that ended the hopes of outsiders Sebastian Langeveld and Matteo Trentin close to the Trouee d'Arenberg sector.
After attacking his main rivals 55km from home, Sagan had outsprinted Swiss champion Silvan Dillier, the last survivor from an earlier break, in the iconic outdoor velodrome in Roubaix after 5hrs 54mins 06sec in the saddle.
"It's really nice to win this race with the world champion jersey".
"Amazing. I'm so exhausted after this race".
The incident happened at a part of the course known as "Hell of the North".
"Peter Sagan was just too good today". In 2017, almost half of the riders did not make it to the finish in the Roubaix Velodrome.