An outbreak of equine flu has forced UK racing to be shut down until February 13, the British Horseracing Authority (BHA) has announced.
Racing's rulers are set to make a further assessment on Monday as to when racing can resume after the virus was detected.
Trainer Donald McCain confirmed on Thursday that he has three confirmed cases in his yard.
Whilst the infected horses had not been racing this week, McCain has had runners at Wolverhampton, Ayr and Ludlow.
As a result, any trainer who ran a horse at those meetings has had restrictions placed on their movement.
No further positive tests have been recorded, but another three days are needed before it will be possible to make a decision on whether it is safe to resume racing as the disease can take that long to show its symptoms.
In a statement, the BHA said: “This approach will allow samples to be collected and assessed by the Animal Health Trust in order that a fully informed decision can be made on Monday.
“This may then allow declarations to take place on Tuesday in time for racing on Wednesday, with 24-hour declarations for all fixtures on this day, should racing be able to resume.
“Declarations for Thursday would revert to the usual procedures.
“Trainers support a precautionary approach and we thank them for the collaborative manner in which they have worked with us to address this unfolding situation.
“This precautionary approach is intended to ensure we put the health of the horse population and control of the virus first, and avoid any unnecessary risk that might come from returning to racing too quickly.
“We appreciate the impact that this may have on the sport commercially, but disease control in order to mitigate the risk of further disruption to the sport – and safeguard the health and welfare of our horses – must be a priority.”
It added that a plan to reschedule this weekend's key races will be constructed.”