The Gold Cup meeting at Scarborough was abandoned on Sunday following two serious incidents involving spectators.
England’s only road race at Oliver's Mount was called off around 3pm before the feature race had taken place.
Police have confirmed that 12 people were injured, with three seriously hurt.
A statement issued by the organisers said: “Today we have had two serious incidents involving a number of spectators.
Our medical personnel, together with the marshals and officials of the club, local police, NHS, ambulance staff and helimeds have treated all the injured.
“In view of the seriousness of these incidents and our requirements to call on outside assistance to help with this treatment, we have reluctantly taken the advice of everyone concerned and have decided to cancel the rest of the meeting.
“We sincerely apologise to you all for taking this decision and hope you will understand our difficulties in this unprecedented situation. The club will be making a full statement in due course.”