Britain's Department of Agriculture, DEFRA, has confirmed a new case of foot and mouth disease close to the site of last month's outbreak in Surrey.
Tests are also being carried out at a farm in the eastern English county of Norfolk.
However, vets ruled out foot and mouth disease being the cause of a sick sheep found at a Scottish livestock market.
The Department of Agriculture is to reintroduce bio-security measures at ports and airports, just days after the state lifted restrictions imposed in the wake of last month's scare.
The new outbreak in England affects a small herd of cattle on farmland in Egham, Surrey, with many of the animals showing symptoms.
A temporary 10km control zone was set up around the farm in southern England following earlier suspicions.
A cull of livestock on the farm is under way. The farm is about 50km from the site of last month's foot and mouth outbreak.
Officials moved quickly this morning to isolate the farm at Egham in Surrey.
The Minister for Agriculture, Mary Coughlan, discussed the latest foot and mouth outbreak with senior officials from her Department in Dublin today.
Minister Coughlan said her officials were doing everything they could to ensure that the animal disease did not reach these shores and a ban is in place on the import of live animals and meat products from Britain.
The minister also said she had been in touch with British Government officials to discuss the situation.
Northern Ireland's Agriculture Minister Michelle Gildernew has announced a return to the 'fortress Ireland' approach adopted after the previous outbreak.
Disinfectant mats will be placed at ports and airports and there will be a ban on imports of cattle from Britain. Already one consignment has been turned away.
The Irish Farmers' Association says the latest outbreak of foot and mouth disease is most alarming.
IFA President Padraig Walshe said his members support the introduction of emergency measures to prevent the disease reaching these shores.
The President of the Cattle and Sheep Farmers' Association, Malcom Thompson, has also expressed concern at the development.
The European Commission had only just decided to lift any remaining trade restrictions on British exports, which had been put in place after the August outbreak. However, it has now moved to re-impose those restrictions.
Britain's Prime Minister, Gordon Brown, has chaired a meeting of his government's emergency committee COBRA.
He pledged that his government would do everything in its power to get to the 'root causes' of the latest outbreak.
