A second outbreak of foot-and-mouth disease is suspected in the protection zone in England where the first outbreak was discovered.
A new herd of cattle has been identified with clinical signs of the disease by Animal Health staff as part of their surveillance activity within the larger protection zone.
Chief veterinary officer Debby Reynolds has ordered that the herd be culled as soon as practicable.
Ms Reynolds said: 'This is a suspicion of foot-and-mouth disease. We have decided to cull these animals. The culling has started. It has been found promptly and I want to continue to assess the situation based on the laboratory test results.'
Experts are also investigating whether the recent floods in England may be behind the outbreak.
Ms Reynolds, said high water levels could have helped spread the virus on the Surrey farm at the centre of the first outbreak.
Tests are still being carried out to confirm whether the nearby Pirbright research site - where the disease was being kept in order to produce vaccine - was the source of the outbreak.
Earlier, Britain's main farmers' union said it is very concerned that the outbreak may have been caused by a possible leak from a nearby laboratory.
The EU has now formally banned exports of British meat and livestock but says it is happy with the way British authorities are dealing with the outbreak.
British Prime Minister Gordon Brown has visited Surrey and told farmers that everything possible was being done to stamp out the latest outbreak of the disease there.
In Ireland, the Minister for Agriculture and Food, Mary Coughlan, has said that she and her officials were closely monitoring developments in Britain.
In a statement, she said she had spoken to her British counterpart, Hilary Benn, and had been assured that the UK authorities were doing all they can to confirm the source of the outbreak and to contain and eradicate it.
She stressed the absolute necessity for all those involved in the livestock industry to remain vigilant and to adopt appropriate bio-security measures at their premises.
Northern Ireland's Agriculture Minister, Michelle Gildernew, has confirmed that the province is to remain exempt from the ban on agriculture exports imposed on the UK.
