The FDA letter warned the eggs may have been contaminated by filth and could be a health hazard. The agency also warned of unacceptable rodent activity.

Bob Langert, a McDonald's vice president, said in a written statement on Friday that McDonald's decision was based on "concern regarding the management of Sparboe's facilities."

McDonald decision also came after Mercy For Animals, an animal rights group, released findings of a three-month, three-state investigation of Sparboe's facilities, which it said exposed unsanitary and inhumane treatment of the animals.

The group's executive director, Nathan Runkle, said Sparboe hired a worker, who really was an undercover investigator for the animal rights group. The investigator "was wired with a pin-hole camera and documented case after case of egregious animal abuse and neglect," he said.

Video on the group's website showed dead hens in cages with living ones, chicks having their beaks broken then thrown into cages, a worker talking about other workers torturing the animals, and living chicks being discarded in plastic bags with dead ones.

"Regarding the undercover videos, the behavior on tape is disturbing and completely unacceptable. McDonald's wants to assure our customers that we demand humane treatment of animals by our suppliers," Langert said.

But he noted that the most alarming actions on video did not occur at Sparboe's Vincent, Iowa, facility, which is the only one that supplied fresh eggs to McDonald's.

Sparboe Farms' website states: "our commitment to food safety, humane animal care and environmental protection are just some of the key ingredients to providing our customers and friends with the highest quality eggs and egg products."

Reuters' call seeking comment was not returned by the company, which says is it is the fifth largest shell egg producer and marketer in the United States.

Last year, more than half a billion eggs were recalled after Salmonella sickened more than 1,000 people, the largest egg recall in U.S. history. The recall did not involve Sparboe Farms.