British investigation into the outbreak:UK government officials believe human error at the private pharmaceutical firm Merial Animal Health is the most likely source for the return of foot-and-mouth disease to Britain, it emerged last night.
As health and safety inspectors began examining the company's labs at Pirbright, Surrey, in southern England, Whitehall sources suggested the potential biosecurity lapse would amount to a breach of procedures rather than negligence.
Senior government officials believe the virus may have been transported by an individual or by a car from the research complex to the farm at the centre of the outbreak about 6km away. If the virus was airborne, it is difficult to explain why other herds closer to the Merial site were not first affected, sources said.
Merial, which researches and manufactures animal vaccines, shares the Pirbright site with the British government's Institute for Animal Health (IAH). It has been established that the strain of the highly contagious virus found in the infected cattle was held by both organisations and was used in a vaccine batch manufactured by Merial on July 16th.
Both the IAH and Merial insisted yesterday that they had good biosecurity procedures which had not been breached.
IAH director Martin Shirley said: "In addition to general checks on biosecurity, which have shown no breaches of our procedures, we have been able to check our records specifically for use of this strain. Our results have shown limited use within the lab within the past four weeks."
The pharmaceutical company also insisted that it was innocent of any wrongdoing: "Our centre operates to the very highest international standards and we insist on stringent adherence to processes and procedures for health, safety and environmental protection, quality control, quality assurance and regulatory compliance.
"While Merial has complete confidence in the integrity of our biosecurity, and our initial investigation shows no breach of our procedures, it is too early in the investigation for anyone to determine the source of the outbreak."
The company's managing director, David Biland, said: "We have been operating from this site for 15 years and during that time have produced hundreds of millions of vaccine doses. In all that time we have never had a breach in our bio-security."
Hopes that the disease would be contained after the initial outbreak were dashed yesterday when a single cow in a second herd was tested positive. The animal is owned by the same farmer, Derrick Pride, whose cattle in another herd tested positive on Friday. The latest identification, relayed to a meeting of the government's emergency committee Cobra - chaired by the British prime minister, Gordon Brown - led to a small extension of the exclusion zone.
Mr Brown insisted the government had acted decisively and clearly to deal with the first outbreak of foot and mouth since 2001. He asked farmers to remain patient during the ban on the movement of cattle, sheep and pigs, which will remain in force for a minimum of 21 days.
The Health and Safety Executive investigation at the site is expected to produce its initial findings on whether Merial was responsible for the leak in the next 48 hours.
Last night, Debby Reynolds, the chief veterinary officer, said it was important to wait for the findings of the inquiry. The Conservative leader, David Cameron, said farmers "had every right to be angry if they were suffering as a result of mistakes by others".
It emerged yesterday there have been a number of warnings that laboratories now at the centre of an investigation are in an unsatisfactory condition and could prove a biosecurity threat.
According to a 2002 report by the government-funded Biotechnology and Biological Sciences Research Council (BBSRC), the Pirbright complex, which was largely built in the 1940s, is in urgent need of investment, and ideally should be totally rebuilt.
"Some of the laboratories and other areas of the Pirbright estate are not close to the standard expected of a modern biomedical facility and are well below that expected of a facility of such importance," it says.
However, Brian Follett, who conducted the Royal Society's reviews of the government's response to the 2001 outbreak, said it was a "gigantic leap" from the deficiencies identified in the report to the leakage of a virus.