The Northern Ireland Executive has appealed for information about illegal animal movements in recent weeks to establish the source of the latest foot-and-mouth outbreaks in the North.
After an emergency session of the Executive, the North's Deputy First Minister, Mr Seamus Mallon, said everyone in the North would suffer unless the Department of Agriculture was furnished with the necessary information.
He said the Executive was drafting contingency plans for the "worst-case scenario". Two cases of the disease have been confirmed in the North in the past three days.
The North's First Minister, Mr David Trimble, said it was essential farmers recognised their collective and personal responsibility, as they were in the front line of defence against the disease.
Two new culls were under way yesterday after suspect secondary outbreaks of foot-and-mouth disease were feared in Ardboe, Co Tyrone, and Newtown Crommelin, Co Antrim.
The North's Minister for Agriculture, Ms Brid Rodgers, said the decision to cull was taken in advance of test results from the Pirbright laboratory.
She announced that all movement of animals in the North would cease and revoked earlier permits. She has also ordered no mixing of cattle and sheep on farms.
Meanwhile Dr Paul Kitchen, head of the Department of Exotic Diseases at Pirbright laboratory in the UK, has criticised the North's Department of Agriculture for making "premature" announcements on foot-and-mouth test results.
"It was, in retrospect, a mistake for the department to give out those preliminary results and perhaps in retrospect it was a mistake for us to tell the department what the preliminary results were," Dr Kitchen said.
In Dublin the Minister for Agriculture, Mr Walsh, said the Government faced its most difficult period in the battle to prevent the spread of foot-and-mouth.
He said he was "extremely nervous" of the situation in the North and announced that the use of marts as assembly points for animals for slaughter would be suspended.
He also said artificial insemination of animals, which is due to resume on Thursday, is being kept under review.
He urged farmers in the State to redouble their efforts to prevent the spread of the disease, adding that there was "anecdotal evidence of a variation in the degree of caution which people are taking".
The Minister of State for Agriculture, Mr Noel Davern, said it was a possibility that some farmers in the North were not reporting suspected cases.
Horse and greyhound racing is being allowed to continue, as they are not susceptible animals, and there are protocols in place which were agreed by the expert group, Mr Walsh said.
If the expert committee makes further recommendations, there may be further restrictions on race meetings, said a Department spokesman.