Experts said the strain was not one recently found in animals, but was similar to ones used in diagnostic laboratories and vaccine production. In a statement, Defra said: "The present indications are that this strain is a 01 BFS67-like virus, isolated in the 1967 foot and mouth disease outbreak in Great Britain." The strain is present at the Pirbright site's Institute of Animal Health and was used in a vaccine batch manufactured last month, Defra said.
A Conservative Party spokesman said: "If there is evidence that this outbreak has come out of Pirbright Laboratory, a full inquiry into the laboratory's bio-security must be carried out urgently and immediately."
Some 60 cattle at the infected farm, close to the village of Wanborough,near Guildford, were culled and their bodies taken away for incineration. Chief Veterinary Officer Debby Reynolds said a cull had also taken place on an adjacent premises which had been identified as having "dangerous contact" with the infected herd.
A UK-wide ban on the movement of all livestock is in place to stop the spread of the disease.