Olympic and world champion cyclist Katy Marchant was taken to hospital after crashing at the Track Champions League on Saturday.
Spectators were also injured after Britain's Marchant collided with Germany’s Alessa-Catriona Propster in the first round of the keirin.
Both riders veered to the top of the banking as they were about to go around a corner of the velodrome. The pair were catapulted over the barriers at speed, landing in the audience.
The event was being broadcast on Eurosport, with the commentator saying "Oh my word!" as the crash happened, before falling silent for several seconds.
Later on the broadcast, a Eurosport reporter at the track said on air that there were no serious injuries among either the riders or spectators, with Marchant suffering a broken forearm.
“We can confirm that two riders and four spectators received medical treatment following an incident during tonight's UCI Track Champions League event at Lee Valley VeloPark, in London,” the International Cycling Union said in a statement.
"The incident took place during the women's keirin race. The event medics responded immediately, with one rider transferred to the hospital.”
British Cycling also put out a statement, confirming the suspension of the event.
"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 also wish to thank the medical staff for their prompt response and ongoing support.
We are working closely with all parties to review the incident before taking appropriate action. No further comments will be made at this time."
The conditions of the riders and spectators were not confirmed by either British Cycling or UCI, with British Cycling noting that Marchant had been taken to hospital for further assessment.
Marchant won the team sprint gold alongside Sophie Capewell and Emma Finucane at the Paris Olympics, and the same trio won gold again in the same event at the world championships in Denmark in October.
AP/ABC