The Pirbright site is shared between the Institute for Animal Health, a government-funded research laboratory, and pharmaceutical company Merial Animal Health, whose work includes manufacturing animal vaccines; both say they have found no evidence of a breach in biosecurity.
The Pirbright laboratories also conduct research into diseases such as variant Creutzfeldt-Jacob disease, avian flu, bluetongue, African horse sickness and salmonella.
Alarm has also been raised about the safety of government labs next-door to laboratories run by U.S.-based private companies such as Merial, and that biosecurity has been breached.
The safety of British science labs in the United States is also an issue, where the safety of their own local laboratories is under question because of the fears of a breach of biosecurity.
The two Pirbright labs have the same level of security as the germ warfare defence establishment at Porton Down on Salisbury Plain, Wiltshire.