Up to 50,000 people are expected to attend the Tullamore Show and AIB National Livestock Show on the grounds of the Charleville Estate in Tullamore.

The event, which showcases Irish agriculture, will have over 1,000 horses taking part in a number of competitions throughout the day, as well as a trade show, cookery contest and livestock show.

Precautions against footand-mouth will be taken at the show despite yesterday's good news from England where a temporary control zone placed around a farm at the centre of a fourth footand-mouth scare was lifted after test results proved negative.

But Britian's chief veterinary officer Debby Reynolds urged farmers to maintain "relentless vigilance" in looking for signs of the disease.

She said the risk of the virus spreading outside Surrey was now "low".

Farmer John Emerson, whose farm also tested negative, said it showed the industry was "not all doom and gloom".

Animals at two farms near Guildford have tested positive for the disease, while animals culled at Emerson's farm inside the surveillance zone set up a week ago were shown not to have foot-andmouth.

Meanwhile, tests of samples from the fourth suspected farm at Wotton, near Dorking, have come back negative. They were sent for analysis after the animals started to exhibit signs of a virus, including runny noses and swollen eyes.

A 3km temporary protection zone which was set up around the suspected case . . .outside the existing 10km surveillance zone . . . has been lifted. The farmer, Laurence Matthews, who believes his calves have pneumonia, said vets had told him they had been "99% sure it was not foot-and-mouth".

The negative tests will come as a boost for the British government which is increasingly confident the outbreak has been contained.

Restrictions on taking animals to abattoirs have been lifted but many movements of livestock . . . such as sending animals to market . . . are still banned in England.

The restrictions have been relaxed further in Wales, with farmers allowed to move animals on welfare grounds.

Reynolds said the overall evaluation was that the "risk of spread outside Surrey was low". She earlier announced the publication of an interim report into the outbreak. It concluded the most likely source of the outbreak was the nearby Pirbright lab site, used by vaccine manufacturer Merial and the state-run Institute for Animal Health.

Asked if the investigation was considering the possibility that the outbreak had been caused deliberately, Reynolds said "every avenue" was being explored.