The government has confirmed that it is investigating another "probable" leak of the foot and mouth virus from Pirbright, the site at the centre of the summer's outbreak of the disease.

There are two facilities on the Pirbright site: one is the government owned and managed Institute for Animal Health, and the other, Merial, a commercial operation that works to synthesise the virus for use in vaccines.

Environment Secretary Hillary Benn issued a written statement saying that investigators have been dispatched to the Merial lab on the site. He said inspectors have been assured that the virus, which escaped through a leaky valve last week, has not escaped into the environment.

Benn said the leak was discovered less than two weeks after Defra (Department for Food, the Environment and Rural Affairs) restored Merial Animal Health's licence to use the virus for vaccine production. On 19 November, some of the virus was found to be missing, and the leak attributed to a broken valve. All operations were immediately stopped and the equipment was decontaminated, he added.

In the summer, the Health and Safety Executive was not able to determine which of the two facilities on Pirbright was responsible for the outbreak of the virus.

Foot and Mouth has an incubation period of up to 14 days, so it will be some time before local farmers will know whether or not the virus was indeed contained. ®

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