An urgent State-wide recheck of all possible contacts sheep or farmers may have had with smugglers or animals from Britain was being carried out last night by Department of Agriculture and Garda investigators.
The hunt for possible infected animals was taking place against the background of the mass slaughter of thousands of animals in a three-kilometre zone around the site of the Republic's first case of foot-and-mouth disease, in Proleek, Co Louth.
As the search continued, farms in Laois, Monaghan, Cavan, Kilkenny, Carlow and Donegal were being sealed off as investigators carried out the most intensive tracing operation seen in the State.
The teams of investigators are working on information gathered over the last three weeks during the hunt for illegally imported sheep and they believe the outbreak in the State will help them in their search.
The Minister for Agriculture, Mr Walsh, referred to the investigation during his briefing yesterday. He said all leads linking any farm with animals imported since February 21st were being followed up. In cases like this, the farmer involved was interviewed and any link, no matter how tenuous, was being followed up "from Donegal to Cahirciveen".
While Mr Walsh said this was normal procedure, the presence of the elite Garda Bureau of Criminal Investigation in the Cooley peninsula indicated the investigations were not routine.
A member of one of the teams said yesterday they were working on the supposition that not all the people they have interviewed had told them the truth about what has been going on.
The fact that the strain of the disease found in Co Louth eluded veterinary experts for so long has shaken confidence in the belief that the disease can be contained. Investigators are "staggered" at the level of smuggling from Britain, which was fuelled by a £15 per hogget profit.
As the EU Standing Veterinary Committee ratified the EU Commission's decision to regionalise the problem in the Republic to Co Louth, allowing exports from 25 counties, Northern farmers lobbied to be given the same treatment.
"If regionalisation is achieved in the Republic, then Northern Ireland must receive the same treatment. Our case is equally valid," said the Ulster Farmers' Union president, Mr Douglas Rowe.
Meanwhile, a second outbreak of foot-and-mouth disease has been discovered in France's Seine-et-Marne region east of Paris, the agriculture ministry announced last night. The first outbreak was discovered in the western department of Mayenne on March 13th.
Britain is bracing itself for a tenfold increase in the number of cases - with a rising total of 4,000-plus cases possible by June.
That was the backdrop to deepening confusion in Britain last night over plans for an extended mass cull to try to curb the crisis now threatening to claim half Britain's total livestock.
The Agriculture Minister, Mr Nick Brown, appeared at odds with the government's chief scientist, Prof David King, and again denied the situation was out of control.
Prof King told the BBC he believed a decision had already been taken to reduce the "report-to-slaughter" time to 24 hours, and to build a two-mile "firewall" around all existing and new areas of infection across Britain.
However, Mr Brown told a press conference no decision had been taken on the chief scientist's advice, and that the government was right to consider the range of options open to it in consultation with "local people with local knowledge".
Prof King bluntly warned the government that if it failed to act quickly "we have quite frankly an epidemic that is out of control" and one which could see the country lose half its livestock.
With 501 cases confirmed last night, and daily increases as high as 70 a day predicted over the next fortnight, the chief veterinary officer finally acknowledged the epidemic was officially worse than that experienced by British farmers in 1967.