British animal health authorities imposed restrictions around a second site amid fears that the outbreak of foot and mouth disease had spread from an initial control zone.
The new zone is just kilometers (miles) away from a research lab in southeast England where two outbreaks of the virus were confirmed last week, and comes a day after officials eased restrictions on transporting livestock.
It is to the west of Dorking, in the same county of Surrey, close to the sites of the initial outbreaks, but outside the surveillance area that was already in place.
"This is a developing disease situation," Debby Reynolds, Britain's chief veterinarian, said in a statement. DEFRA, the agriculture ministry, said that the zone was imposed after an "inconclusive assessment of clinical symptoms" by veterinary staff.
"The containment and eradication of FMD remains our priority. This is why we have moved swiftly to put in place a Temporary Control Zone while we investigate this development. At this stage disease has not been confirmed, laboratory results will follow." Aside from the two confirmed cases at Pirbright in the past week, and the new zone, results were also expected soon from another suspected outbreak which occurred close to Pirbright.
So far, nearly 600 animals have been slaughtered since the initial outbreak.
On Thursday, the government-run Institute of Animal Health (IAH) which shares Pirbright with private drug company Merial Animal Health, which is owned by US drugmaker Merck and France's Sanofi-Aventis, insisted that it was not to blame for recent outbreaks of the virus. The IAH instead suggested that Merial should be under greater scrutiny.
"We have previously reported that the Institute for Animal Health works only on small volumes of virus whereas vaccine production by Merial is one million times greater," IAH director Professor Martin Shirley told reporters.
"All of our checks have shown this treatment facility to have been working appropriately at all times. We would be surprised to learn of the presence of any virus in the soil around our drains." The BBC reported on Thursday evening that part of the Merial facility was built on land that was considered to be at "substantial risk" of flooding, in breach of government guidelines.