The Polish Department of Agriculture has revealed that its investigations into the source of horse meat at meat plants in the country have so far proved negative.

Deputy General Veterinary Inspector Jaroslaw Naze told RTÉ Radio that the six meat plants that were identified as supplying beef to Ireland and England have been investigated.

Mr Naze said samples taken at those plants have not proved positive for horse meat.

He said that its investigation is continuing and he will have a final report to send to his Irish counterparts next week.

Minister for Agriculture and Food Simon Coveney said last Saturday that the source of the horse meat supplied to the Silvercrest plant owned by Larry Goodman was a plant in Poland.

Mr Coveney said that he had informed the Polish authorities and that the Department of Agriculture investigation would be wound down.

Mr Naze said that the plants investigated in Poland were only approved to process beef and not horse meat.

He also said that the plants at the centre of the controversy were totally Polish-owned and had no Irish connection.

The Irish Cattle and Sheep Farmers' Association has called on the ABP Food Group, which owns Silvercrest, to confirm whether the source of horse meat in its frozen burgers was from Poland.

ICSA President Gabriel Gilmartin said: "We need clarity on this issue as a matter of urgency and I would call on ABP to issue a statement confirming that the source of the contaminated burger ingredients was in fact Silvercrest's Polish supplier, and that it did not come from another, unknown, source."

Elsewhere, Mr Coveney said today that there is no evidence to suggest that the finding of horse DNA in frozen beef burgers is going to have a long-term negative impact on the reputation of the Irish food industry.

He said consumer opinion data collected by Bord Bia over the past three weeks in Britain indicates that people are making a distinction between one single cheap frozen beef product and the broader Irish beef industry.