Though it initially made "absolute assurances" that all of its burgers were 100% beef, Burger King has been forced to admit that some of its patties may have contained horse meat, after traces of equine DNA were found at one of their processing plants.

The scandal started two weeks ago, when supermarket chains in the UK and Ireland began pulling certain beefburger products off the shelf after test concluded that they contained varying amounts of horse meat.

The tainted product was traced back to three processing plants, one of which — Silvercreft Foods — supplies Burger King restaurants in both the UK and Ireland with some of their patties.

"Our independent DNA test results on product taken from restaurants were negative for any equine DNA," the company said in a statement. "However, four samples recently taken from the Silvercrest plant have shown the presence of very small trace levels of equine DNA."

The statement went on to say that Silvercrest had imported adulterated beef from a "non-approved supplier in Poland," despite promising the company "to deliver 100% British and Irish beef patties."

As a result, Burger King has stopped doing business with Silvercrest, and has hired a new suppliers based in Germany and Italy.

"While the Food Safety Authority of Ireland has stated that this is not a food safety issue, we are deeply troubled by the findings," said the company's vice president of global quality, Diego Beamonte.

[photo via AP]