Chickens can pass the bacteria to eggs because the eggs leave hens through the same passageway as feces, according to the U.S. Department of Agriculture's Food Safety and Inspection Service.

CNN: STORY HIGHLIGHTS

Jacque Knight, a spokeswoman for the U.S. Department of Agriculture's Food Safety and Inspection Service, said federal officials are going over records at the Columbus, Nebraska, plant where the meat was produced and that the recall could grow even more.

CNN: Recall of frozen hamburger patties doubles