Grand National winning horse trainer Donald McCain has confirmed the three horses to test positive for Equine Influenza are from his Cheshire yard.
The outbreak has forced the cancellation of all British racing on Thursday, after three horses tested positive for equine influenza, despite having been vaccinated against it.
The British Horseracing Authority (BHA) confirmed the affected stable had runners at Ayr and Ludlow on Wednesday, where they were in close proximity to dozens of other horses from many racing stables.
It said the cancellation was 'a precaution' and humans are not at risk from the virus.
In a statement, McCain said his Bankhouse stables had had three confirmed cases.