AGRICULTURE Minister Simon Coveney has said his department is looking at domestic ingredients as well as imported ones as the possible source of horse-meat contamination in burgers.
The revelation came as it emerged that Mr Coveney had received further test results in the contaminated burger investigation.
However he refused to disclose them until he had cross checked them with further results due today or tomorrow.
"I am not sitting on anything. We got the latest batch of results this evening but I am not going to give any news on test results until I am sure I can stand over those results," he said.
The results are believed to relate to an imported ingredient used to make burgers at the Silvercrest plant in Co Monaghan.
Mr Coveney also moved to dampen fears that the contaminated burgers could contain the cancer-causing drug phenylbutazone after the matter was raised in the House of Commons yesterday.
Mr Coveney said the Food Safety Authority of Ireland (FSAI) had tested burgers containing horse DNA for phenylbutazone but all were clear of it.
Britain's shadow environment minister Mary Creagh told the UK parliament that several horses slaughtered in Britain last year tested positive for the carcinogen phenylbutazone, which is banned from the human food chain.
While the investigation into how Irish burgers were contaminated with horse meat was last week centred on an imported ingredient, Mr Coveney confirmed yesterday his department was probing a number of possible sources.
There were 40 different suppliers of ingredients to the ABP Silvercrest processing plant in Co Monaghan, where burgers containing up to 29pc horse meat were found.
"We need to follow the track as to where all of that product came from; we need to get samples of all the ingredients that went into burgers," he said.
He said his Department had to put together a "very complex jigsaw" to find a common ingredient to all of the problem burgers and that process took time, he said.
The Irish Farmers' Association has accused the FSAI of handling the horse DNA controversy badly.