Cyclist Stig Broeckx is in a coma after suffering two bleeds on his brain in a collision involving two motorbikes.
Broeckx was one of 19 riders affected by the incident that occurred on stage three of the Tour of Belgium on Saturday.
The accident, which happened near the city of Verviers, forced the stage to be abandoned.
The crash comes two months after fellow Belgian cyclist Antoine Demoitie was killed after a collision with a motorbike in the Gent-Wevelgem one-day race.
Broeckx's team, Lotto-Soudal, previously confirmed he had been taken to hospital, and - providing an update - team doctor Servaas Binge said: "It was immediately clear that Stig had incurred a head injury and that he needed to be transported to a neurosurgical centre.
"Together with the race doctor and the medical emergency team we decided to transport him to the hospital of Aachen, which has the necessary infrastructure. A scan was taken at the hospital and it showed that Stig has two bleedings in his brain.
"Stig is in a non-induced coma, but for the moment he doesn't need to undergo surgery. He doesn't have a skull fracture, but he does have a fractured eye socket, which will be further evaluated later.
"At this point, it is very difficult to give a prognosis about a full recovery. The next 24 hours he will be very closely monitored."
Confirming Lotto will not compete in the fourth and final stage, team manager Marc Sergeant said: "Of course we are very shaken by all that has happened. Last year our team had very difficult moments after the accident of Kris Boeckmans, exactly three months ago Stig was already hit by a motorbike in Kuurne and a few weeks later the peloton had to cope with the death of Antoine Demoitie.
"This is very hard for all staff members and riders, but even more for the family and friends of Stig. We can only hope that there is a positive evolution in the condition of Stig and we will support him and his family the best we can, both medically and emotionally.
"After the neutralisation, the riders gathered in the team bus and drove to the team hotel were they stayed together to support each other and to talk about what happened. After deliberation we informed the organisation that we won't ride the last stage of the Belgium Tour.
"At the moment it is pointless to make any accusations, but it should have been obvious much longer that structural measures concerning the safety of the riders are necessary."
The UCI have confirmed it will look into the incident to determine whether the rules regarding the conduct of motorcycle riders in races were respected.