The Department of Agriculture is sending more samples from Co Louth to a foot-and-mouth lab in England for tests.
The samples were taken from sheep on a farm at Tiedmont. The farm is just inside the 10-kilometre zone from Proleek, site of the only outbreak in the Republic.
The Department said it was more concerned about this incident than anything else reported in the country over the past few days. Vets in the area were also reported to be "very concerned" about the suspect sheep.
A Department spokesman said: "Samples have been taken from sheep and are being sent to foot-and-mouth experts in Pirbright, Surrey.
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"We expect to hear the results of an analysis of the samples by Friday morning," the spokesman said.