The Cheltenham Festival next week has been threatened by a suspected case of foot-and-mouth disease at the Lambourn stables just five km from the course.
"The [British] Ministry of Agriculture has confirmed that there is a suspected case in the Lambourn area," said the chairman of the Lambourn Trainers' Association Peter Walwyn.
"It has not been confirmed but it is obviously a big worry."
A farm eight km from the course was cleared of foot-and-mouth disease this week.
Clerk of the course Simon Claisse said a case of foot-and-mouth would jeopardise the highlight of the jump racing season scheduled for March 13th-15th.
"We've said from the outset that if another major training centre was hit by the disease then that would be a major blow to the sport going ahead," he said.
Irish trainers have already decided not to attend the meeting and French horses are unlikely to make the trip.
Racing resumes in England today after a week-long suspension but events at Hereford, Chepstow, Carlisle and Towcester have been cancelled because they fall within infected areas.