This is a useful warning that we're not out of the woods and have to keep up our guard

Margaret Beckett Environment Secretary

Suspect lesions were found in the mouths of two sheep at Mount Pleasant Farm in Hawnby, near Thirsk.

The county was badly affected during the outbreak, suffering 135 cases before the disease petered out in September last year.

Now all livestock movements have been halted within a five-mile (8km) radius, and government vets are inspecting four other farms in the county which supplied the farm with sheep.

Speaking to BBC News, Mrs Beckett said she hoped the intitial negative test results on two sheep would be confirmed by further analysis in the next 96 hours.

Lambing season

"Let's hope it turns out not to be foot-and-mouth, but this is a useful warning that we're not out of the woods and have to keep up our guard."

Mrs Beckett said the UK could not be "absolutely confident" that every last possible source of the disease had been eradicated, especially until farmers got through the other side of the lambing season, when animals will be more at risk.

Rosey Dunn, vice-chairman of the York County branch of the National Farmers' Union (NFU), said the initial test results would come as a massive relief to farmers.

She said: "Obviously it's great news, I'm absolutely delighted for the local area, so far so good.

"We shall have to wait for the final results but I am sure they will confirm what we expected and that's a negative. We can all breath a huge sigh of relief."

The National Farmers' Union (NFU) has also said it is "cautiously optimistic" that samples from the two slaughtered sheep will test negative for the disease.

The lesions were discovered on Tuesday by government vets carrying out an inspection visit required when farms restock.

The government emphasised the vet involved had not said he thought the animals had foot-and-mouth, only that he could not rule out the possibility.

Disease-free status

The lesions could have been caused by other conditions which can affect sheep.

But any return of the disease would devastate the farming industry, tourism and the countryside, and could mean Britain losing its disease-free status within the EU.

The tests are being carried out at the Institute of Animal Health laboratory at Pirbright in Surrey.

Animals are routinely checked by vets when farms restock

All animals at the farm were slaughtered during the previous foot-and-mouth outbreak when the disease hit a neighbouring farm, but it was never found there or at the farms from which the two sheep had been bought, he said.

Defra officials were still turning vehicles away from Mount Pleasant Farm on Wednesday morning.

Neighbouring farmer Ian Woodhead, who has just begun restocking after his own livestock were culled last summer, said news of the initial test result was "just what we wanted to hear".

He added: "I realise there's another 96 hours until it's finally confirmed, but if they've come out with this initial negative result as quickly as this it's very encouraging indeed."