Minister for Agriculture Simon Coveney has said that results of tests into the source of horse DNA in burgers show that it came from ingredients imported from Poland.
Mr Coveney confirmed that results received overnight had been positive, with three samples containing significant levels of horse DNA.
All three of these burgers had a common ingredient that had been imported as a raw material from Poland by Silvercrest Meats in Ballybay, Co Monaghan.
Mr Coveney said this was the only ingredient so far to have tested positive for horse DNA.
He also reaffirmed that tests on samples taken from Irish food ingredients were negative and he said he was pleased that the integrity of Irish food production was maintained.
The Department of Agriculture has said that further tests of the Polish ingredient have been released and are showing "up to 20% horse DNA content relative to beef".
Mr Coveney said he had spoken to the company and asked them to undertake a number of measures, including sourcing all future ingredients from Ireland and England only.
Tesco, which withdrew from sale all products supplied by Silvercrest, said in a statement that the source of horse DNA identified by the department correlated with the results of its own investigations at the plant.
Meanwhile, Burger King has released a statement confirming that tests on Silvercrest products produced for the chain had detected no horse DNA.
The fast food outlet stopped sourcing burgers from the Co Monaghan company last week as a precautionary measure.
The burgers had previously been used to supply Burger King outlets in Ireland, Britain and Denmark.