Polish food processing plants are believed to be the source of horse-tainted hamburger meat recently discovered in the United Kingdom and Ireland, according to the Food Safety Authority of Ireland (FSAI).

The Dublin-based Silvercrest meat processing plant, which supplied burger meat to national supermarket chains and to hamburger giant Burger King, among other clients, had received imported meat from Poland, the FSAI reported in a Jan. 28 press release. Since the FSAI discovered equine DNA in beef patties on a routine investigation, the Minister for Agriculture, Food, and the Marine has been carrying out additional tests to pinpoint the source of the DNA.

Investigators determined that there were "significant levels of equine DNA (4.1%) in raw material that was used in the manufacture of burgers," the FSAI stated.

"The Minister said he was confident that this finding leads to a firm conclusion that the raw material in question was the source of equine DNA introduced into burgers manufactured at Silvercrest," the organization said. "The FSAI welcomes these conclusive results, which are in line with the results found by the FSAI during its survey into some beef burger products on sale in retail shops in Ireland. The FSAI has notified the Polish authorities and the matter is now with them