Preliminary results of tests on samples taken from a sheep showing signs of foot-and-mouth disease at Irish Country Meats plant in Navan, Co Meath, are expected tomorrow.
A major security operation was launched after the sheep, from a farm at Kilcogy in Cavan, was found to have a blister on its lip.
Tissue samples from the animal were prevented from being sent to the Pirbright laboratory in Surrey, Britain yesterday by the Aer Lingus dispute at Dublin Airport. They were finally brought to Heathrow by another carrier.
A number of plant staff and farmers are being kept at a Navan hotel as a precautionary measure. The plant was sealed off and disinfected immediately.
The remaining staff who had no contact with the animal were sent home and told not to report for work yesterday.
The plant is expected to be shut until Tuesday.
However, a Department of Agriculture spokesman said the case was not one of "major concern".
The Minister for Agriculture, Mr Walsh, said Garda inquiries were ongoing into the tracing of sheep. He said the authorities were now getting information on movements.