THE contamination of beef burgers with horse meat was probably accidental, according to the food safety watchdog.
The disclosures, in a highly disturbing Food Safety Authority of Ireland (FSAI) report, could affect Ireland's extremely valuable exports -- worth €2bn every year.
Supermarkets scrambled to take burgers that could contain horse meat off their shelves while demanding answers from their suppliers as to how it had happened.
Two leading Irish meat processing plants are at the centre of a probe after the beef burgers they produced were found to contain other meats.
One of the plants, Silvercrest in Monaghan, is owned by magnate Larry Goodman. Silvercrest issued a statement blaming European suppliers.
The second plant, Liffey Meats in Cavan, is owned by the Mallon family.
Raymond Ellard, director of consumer protection with the FSAI, told RTE this morning: "We know the companies do not buy or handle horsemeat. So if this happened, more than likely it's been accidental."
More than one in three of the burgers sampled -- or 10 from from a total of 27 -- had traces of horse DNA.
The horse DNA was found in almost 30pc of the meat content in one sample of burgers from Tesco.
Twenty-three of 27 burgers had traces of pig meat. The probe also tested ready meals, including beef lasagne and cottage pie, finding pork in 21 out of 31.
Additives sourced from abroad and used to bind the meat were suspected to contain the horse DNA, according to Agriculture Minister Simon Coveney.
Further tests are now under way at the two meat processing plants to determine if other meat products were contaminated.
Department officials are interviewing management at the companies and checking papers to establish the source of the horse meat.
However, it is unlikely that the companies involved will face any penalties as it appears there has been no breach of food safety laws.
The FSAI said there were no public health concerns, but it could not rule out an investigation into other meat processing plants.
Traces of horse DNA were also found in burgers produced by UK company Dalepak Hambleton which supplies Iceland. In total there were nine companies whose beef burgers were found to contain pig meat, with three of the companies also producing burgers containing horse meat.
Mr Ellard said: "We may decide now we need to do more checks but it's not confirmed yet if it's necessary or what we'd be looking for.
"The processors have gone into overdrive to get to the bottom of it. We haven't put a deadline on them. We're satisfied they're taking a very professional attitude."
He said the companies did not process horse meat, and that the FSAI did not think they were simply attempting to use cheap meat to produce burgers.
He added: "We don't think there's widespread skulduggery."
Chief executive of the FSAI Professor Alan Reilly said that imported ingredients may be to blame.
"If the ingredients have been imported from countries where they process horse meat, and they also process beef meat in the same plant, then you could get cross-over contamination between the two species," he said.
Larry Goodman's firm ABP, which owns Silvercrest, also supplies major fast-food retailers including Burger King in the UK but insisted that this product was not affected as they were on separate supply lines.
It said it had taken "immediate action" to withdraw all the suspect product.
"Silvercrest has never purchased or traded in equine product and has launched a full-scale investigation into two continental European third-party suppliers who are the suspected source of the product in question," it said.
Liffey Meats withdrew all products identified by the FSAI tests, and also said that it believed imported ingredients were the source of the contamination.
These would be replaced with other sources before production resumed, it added.
"We sincerely regret that any product produced by the company would not conform to the highest specifications and sincerely apologise to our customers," it said.
Tesco said it would not take any stock from affected suppliers until the investigation had a "satisfactory resolution". Aldi and Lidl have also launched separate probes.
Food exports are worth €9bn to the Irish economy, €1.9bn of which comes from the beef sector.
"In the food industry, reputation is everything," Mr Coveney said. "Stories like this are not helpful."