A suspected case of foot-and-mouth disease has been discovered 30 miles away from the last outbreak in Surrey.
The government has set up a three-mile exclusion zone in the Egham area around the affected site and a pre-emptive slaughter of cattle has been ordered.
Prime Minister Gordon Brown is due to chair a meeting of the Cobra emergency committee at 1700 BST.
A report into the previous outbreak blamed a leaking pipe at the nearby Pirbright animal research site.
Samples from the suspect farm are undergoing initial tests. The Cobra meeting will take place once the government has received the results.
Earlier in the summer, two farms tested positive for the disease but the all-clear has since been given.
Foot-and-mouth was confirmed in a herd of cattle at Woolford Farm in Surrey on 3 August.
A second case, at a farm nearby, was confirmed on 7 August.
On 7 September, the government declared Surrey to be foot-and-mouth free.
Article first appeared on the BBC Website.
The last outbreak occurred in August.