A third outbreak of foot-and-mouth was feared last night, but Debby Reynolds, the chief veterinary officer, announced a partial lifting of the national ban on the movement of cattle to ease fears of a meat shortage in shops at the weekend.
Ms Reynolds has ordered a cull at a farm inside the existing 3km protection zone around two affected farms in Surrey because of suspicions that more cattle have become infected with the highly contagious disease. A third farm in the village of Normandy has fields adjoining the second farm to be infected.
All cattle at the second farm were culled on Tuesday. Ms Reynolds said: " I have ordered a culling on suspicion of foot-and-mouth on a farm adjacent to the second infected premises."
Meanwhile, workers at the Pirbright labs which are suspected of a leak which led to the outbreak, were being interviewed by security officials to rule out the possibility that it was done deliberately as an act of bioterrorism.
Ministers are awaiting a definitive report from the Health and Safety Executive on soil samples taken from the drains at the private labs of Merial, the US-based vaccine manufacturer on the site. HSE investigators were also checking showers at the premises.
The partial lifting of the travel ban from midnight raised hopes for other farmers outside the 3km protection zone and 10km surveillance zone near Guildford that they can get back to "business as usual".
They will be allowed to resume sending their animals for slaughter to abattoirs with strict biosecurity measures and they can arrange for the collection of dead animals from farms, but farmers' markets and the movement of animals across roads are still banned.
The partial lifting of the ban came after warnings that retailers could start running out of meat at the weekend. Ministers and farmers are keeping their fingers crossed that, in spite of a suspected third outbreak, the partial lifting of the ban will herald the beginning of the end of the crisis.
The chief veterinary officer admitted there was a "low" risk that the disease could still spread to the rest of the country.
"It is my view that the emerging conclusions of the epidemiological work and the ongoing testing indicate there is a low but not negligible risk of the spread of foot-and-mouth disease from the protection and the surveillance zone to the rest of the country," she said.
She denied that the decision partially to lift the ban was driven by financial pressures on the Government, which is facing claims for millions in pounds in compensation from farmers. "Absolutely not," she said "This is based on my veterinary assessment."
Farmers are still prevented from exporting their meat for the next three months under Monday's EU ruling, but there may be moves to have it lifted early.
Asked if she now believed that the situation was under control, Ms Reynolds said that it was still very early. She added: "We have got two infected premises and a new premises that has been culled on suspicion."
Peter Ainsworth, shadow Environment Secretary, said: "The news that further culling is to take place in Surrey will come as a bitter blow to the farmer concerned and he has my deepest sympathy. The fact that the need for this arises from a dangerous contact, however, suggests that the disease is not spreading widely - but we can only wait and hope at this stage."
The president of the National Farmers' Union, Peter Kendall, described the easing of the ban as a "measured and very necessary first step on the road towards getting the industry back to normal and maintaining supplies of home-produced meat to consumers". He added: "It is as vital as ever that livestock farmers remain vigilant, check their stock regularly and report anything suspicious immediately. The highest possible standards of biosecurity must be maintained."
He indicated that discussions were taking place between the NFU and Hilary Benn's Department for Environment Food and Rural Affairs aimed at a further easing of the ban to allow some farm animals to be moved on welfare grounds.
"We recognise there are growing concerns over animal welfare, ranging from cattle due to calve away from the farm, through shortages of forage to pigs needing to move to suitable housing after weaning," Mr Kendall said yesterday.