Racing was abandoned in the Track Champions League at Lee Valley VeloPark in London after British Olympic champion Katy Marchant and another rider crashed over the barriers into the crowd.
Marchant and German rider Alessa-Catriona Propster left the track at speed along with their bikes and collided with spectators.
British Cycling said the two riders and four supporters were treated by event medics and Marchant was taken to hospital.
In a statement, British Cycling added: “WBD Sports, British Cycling, Lee Valley VeloPark, and the Union Cycliste Internationale unanimously decided to suspend all further racing for the evening and want to extend their best wishes for a speedy recovery to both riders and all affected spectators.
“We are working closely with all parties to review the incident before taking appropriate action.”
At the same venue at the 2022 Commonwealth Games a high-speed collision involving several riders resulted in England’s Matt Walls being catapulted over the barriers into the crowd with his bike.
The London venue installed a 1.4-metre barrier, costing £250,000, around the track this year.
Thirty-one-year-old Marchant, who won Team Sprint gold at the 2024 Paris Olympics, was competing in the second heat of the women’s keirin.