Belgian cyclist Antoine Demoitie has died after he was hit by a motorbike following a fall during the Gent-Wevelgem race on Sunday.
The 25-year-old, a member of Belgian team Wanty-Groupe Gobert, fell around 150 kilometres (90 miles) into the race in Sainte-Marie-Cappel - during a brief crossing over the border from Belgium into northern France.
He was then hit by a motorbike while on the ground, before being transported to a hospital in Lille where he succumbed to his injuries.
Regional police spokesman Frederic Evrard: "The rider died. An inquiry is under way to determine the circumstances."
The Gent-Wevelgem cobbled classic saw riders battling strong winds as they tackled 10 climbs over a 243km route.
Former Belgian national champion Jens Debusschere was also hospitalised after he sustained a concussion following a heavy crash, his Lotto-Soudal team said.
The International Association of Professional Cyclists (CPA) said on Monday that they wanted "light to be shed upon the circumstances" of Demoitie's accident.
"In this moment of grief and sorrow we do not want a debate, but we do feel a lot of frustration," said CPA president Gianni Bugno.
"We have always maintained that the cyclists' safety must be first in the discussions of the different key players in cycling.
"We do not want to accuse anyone, but to reflect on the responsibilities of everyone to ensure that attention, awareness and control over safety standards are maintained to a very high level."
A statement on the UCI website read: "The Union Cycliste Internationale (UCI) is extremely saddened to learn about the passing of Belgian rider Antoine Demoitié of Wanty-Groupe Gobert."
"Antoine will be truly missed", said UCI President Brian Cookson. "Our thoughts are with his family, friends and team."
The race, which includes two ascents of the hills of Kemmelberg, was won by Slovakia's Peter Sagan.
His team has withdrawn from the Three Days of De Panne race, which starts in Belgium on Tuesday.