Burger King admitted on Thursday night that the company has used horsemeat in burgers and whoppers at its UK and Ireland locations, The Daily Mail reported.

Previously, though, the fast food chain repeatedly insisted that its products never used the meat - but tests proved their guarantees wrong, according to The Daily Mail.

The horse DNA reportedly came from chunks of meat imported from the Poland-based processing plant, Silvercrest Foods, under investigation by the Food Safety Authority of Ireland, WebProNews.com reported. Besides equine DNA, the investigation also uncovered pig DNA in Silvercrest's products. While Burger King told WebProNews.com that the meat tested in its restaurants was negative for horse DNA, the company admitted it has used meat from Silvercrest, and has since changed its supplier.

"Our independent DNA test results on product taken from restaurants were negative for any equine DNA," Burger King said in a statement issued to The Guardian. "However, four samples recently taken from the Silvercrest plant have shown the presence of very small trace levels of equine DNA. Within the last 36 hours, we have established that Silvercrest used a small percentage of beef imported from a non-approved supplier in Poland. They promised to deliver 100 percent British and Irish beef patties and have not done so. This is a clear violation of our specifications, and we have terminated our relationship with them."

Diego Beamonte, vice president for global quality at Burger King, told The Guardian that the company is "deeply troubled by the findings of our investigation and apologize to our guests, who trust us to source only the highest quality 100 percent beef burgers. Our supplier has failed us and in turn we have failed you."

He added that it's not customary to test for equine DNA in the production of beef, but the company would examine whether enhanced controls are needed in the future.

As a precaution, according to USA Today, Burger King said it is now using suppliers from Germany and Italy.