PIRBRIGHT, England -- Biosafety experts scoured a high-security animal laboratory in rural England on Sunday to determine how a strain of the foot-and-mouth virus may have escaped from a facility dedicated to eliminating the devastating animal disease.
Officials increasingly suspect that the lab -- home to a government research center and a company that makes foot-and-mouth vaccine -- was the source of the outbreak on a nearby farm. That has raised hopes that the disease was not spread by other animals and could be contained.
The particular strain of the highly infectious disease was identical to one used at the lab and had not recently been seen in live animals, the agriculture department said.
Prime Minister Gordon Brown said he was hopeful that a potentially disastrous livestock epidemic could be averted.
"The first thing, having identified a possible source of the disease, we must now look at the transmission mechanism," Brown said, adding that the government has not ruled out other sources.
Britain has banned exports of livestock, meat and milk and halted the movement of cattle, sheep, goats and pigs nationwide to prevent the spread of the virus. The United States and Japan immediately banned British pigs and pork products.
The case is the first in Britain since 2001, when carcasses of the 7 million culled cattle were burned on huge pyres that dotted the countryside. The farming industry was devastated and rural tourism was badly hit.
The affected farm is about 4 miles away from the lab, which is shared by the government's Institute for Animal Health and a private pharmaceutical company, Merial Animal Health, the British arm of Duluth, Ga.-based Merial Ltd.
The agriculture department ordered a 6-mile protection zone set up around the lab and the farm. It also began an urgent review of biosecurity measures at the lab. Experts from the Health and Safety Executive were inspecting both the Merial and government facilities.
Cattle on the farm outside Wanborough, 30 miles southwest of London, tested positive for the disease, which affects cloven-hoofed animals including cows, sheep, pigs and goats. All livestock at the farm were slaughtered Saturday, as well as animals at a second farm nearby.
The disease, which does not affect humans, can be transmitted though contact between animals or by wind.
The agriculture department said there had been no movements of livestock from the affected farm since July 10, further raising hopes that the situation could be contained. The Department for Environment, Food and Rural Affairs, or DEFRA, said the strain was present at the government lab and was used in a vaccine batch manufactured last month by Merial Animal Health.
Merial suspended manufacture of the vaccine as a precaution, but insisted Sunday its plants "operated to the highest level of product quality and safety."
Martin Shirley, director of the Institute for Animal Health, said the strain had been in "limited use" within the institute's own laboratory in the past four weeks but an investigation had found no breaches of biosecurity procedures.
"There are other possible sources of the virus, but they are looking pretty remote," microbiologist Hugh Pennington told the British Broadcasting Corp. "It may not be a huge security breach. It may just be one incident which let a puff of virus out."