There are questions to be answered as to how 248 lambs were processed at a plant in Athleague, Co Roscommon, after passing through a farm in Armagh, the Minister of State for Agriculture, Mr Noel Davern, has said.
And the president of the Irish Farmers' Association, Mr Tom Parlon, has proposed that the "full rigours of the law" be used against any farmer, dealer, meat-processor or other person found to have breached the regulations on the movement and sale of animals.
Mr Davern told RTE Radio's Morning Ireland programme yesterday that the Department was "not happy with the answers we're getting."
He confirmed that "a person involved in the whole transaction" had gone missing. Asked if this was the farmer who delivered the lambs to the Kepak plant, he said: "I wouldn't say you're too far wrong in that."
Mr Davern blamed the IFA for sheep not being tagged in the Republic. The association had been resisting this for years, he said.
Asked if it was not incumbent on meat plants to refuse untagged British lambs, he said he did not want to prejudice the case.
The Department was receiving conflicting information. "We have to be very careful not to prejudice the case. We have to ensure that anybody who has endangered our health status in this country should be fully prosecuted," he added.
On the RTE Radio 1 Morning Ireland programme yesterday Mr Parlon said: "All the genuine farmers who have been taking precautions, and who are now extremely worried, are getting very, very vexed that the whole integrity of the food industry has been breached by a small number of individuals.
"The difficulty we have in the single market now is that all the borders are being broken down," he said.
Irish farming was already "very beleaguered" and a foot-and-mouth outbreak would be "the absolute nail in the coffin".