The fast food chain said in a statement that it had dropped Silvercrest Foods as a supplier for its U.K. and Ireland restaurants as a "voluntary and precautionary measure."
Last week Silvercrest shut down its production line and recalled 10 million burgers from supermarket shelves in Britain and Ireland after horse DNA was found in some beef products.
Products from another Irish firm and one in Britain also were contaminated.
Irish food officials say an ingredient imported from an unspecified European country is the likely culprit.
Officials say there is no risk to human health, but the episode has raised food security concerns.