The Food and Drug Administration found traces of listeria at a Kellogg Co. bakery in Augusta, Ga., during an inspection earlier this year.
In a letter released Tuesday, regulators say that the pathogen was found in several spots along the production line that comes in direct contact with food. The FDA also noted other problems at the plant such as insects near areas where food is located.
Kellogg said it has undertaken a number of aggressive actions to address the concerns and is confident in the safety of its food.
The company, based in Battle Creek, Mich., makes a variety of Keebler and Famous Amos cookies at the Augusta plant.
Kellogg voluntarily shut down the plant after the FDA identified the problems in February and completed a comprehensive cleaning. The company said it also has made a number of other updates to address the concerns, such as flooring repairs and roof improvements.
Kellogg said it is in the process of making a number of other longer-term upgrades to its equipment and infrastructure there.
The issue is a source of serious concern for Kellogg after its business took a major blow last year from the impact of a major cereal recall and problems at another plant that led to a shortage of Eggos.
While the FDA noted that the finished cookies from the Augusta plant don't support the growth of listeria, its testing indicated unsanitary conditions.
Listeria is an organism that can cause serious and sometimes fatal infections in young children, elderly people and others with weakened immune systems. Symptoms include high fever, severe headache, stiffness, nausea, abdominal pain and diarrhea.
Shares of Kellogg fell $1, or nearly 2 percent, to $54.41 in midday trading.