Race organisers told Cyclingnews that the crash occurred on a descent some 65km into the stage, when one motorbike collided with another that was at a standstill, sending both into the bunch of riders. The stage was initially neutralised and then abandoned altogether.
The Cofidis team reported that 19 riders were involved and that 11 of them were taken to hospital. Several of those riders reported on HLN.be to have been involved in the incident include Jesper Asselman (Roompot Oranje Peloton), Pieter Jacobs (Topsport Vlaanderen-Baloise), Tony Hurel (Direct Energie) and Loïc Chetout (Cofidis, Solutions Credits). The extent of the injuries have not been confirmed.
Among the most serious seems to be Lotto Soudal's Stig Broeckx, who has reportedly taken a blow to the head and has been taken to Aachen hospital. The Belgian rider was hit by a moto earlier this year at Kuurne-Brussel-Kuurne.
Several images have been captured of the incident and the neutralization of the stage, and posted to Twitter.
The UCI posted a statement on Twitter regarding the new rules that it introduced regarding the conduct of motorcycles in races, and wrote that it would look into the incident to determine if those rules were broken.