(CNN) -- Most air travelers have encountered something gross on board planes at one time or another, like old food crumbs or stained seats. But now comes this: rodent droppings in the cabin.
The U.S. Food and Drug Administration sent a warning letter to Delta Air Lines last week after inspectors found "the presence of rodent excreta pellets and rodent urine stains" near the food preparation and storage areas of one of the carrier's planes.
The inspection -- conducted from January 26 to February 2 in Atlanta -- revealed droppings "too numerous to count" in the ceiling panels of the plane's middle crossover galley, or directly over places where food and drinks are stored, according to the letter.
There were also rodent droppings above the door panels in the forward galley, where food is prepared by flight personnel, according to the letter.
The plane was pulled from commercial service, and the issue was resolved within a few days, Delta said in a statement.
"This clearly was an isolated incident, and we cooperated with the FDA immediately to resolve it earlier this year," said Ashley Black, a spokeswoman for the airline.
"The health and safety of Delta's customers and employees are Delta's top priority. We take this issue very seriously and have an established routine servicing program to inspect our aircraft."
Black declined to answer any other questions, including whether the problem involved rats or mice, how the issue was resolved and what kind of plane had the rodent activity.
The government's warning letter, dated April 13, asks Delta to outline the specific steps it has taken to correct the violations, including an explanation of how it plans to prevent them from happening again. The airline has 15 days to respond.
"We believe a recurrence is likely without adequate preventive measures in place," wrote John Gridley, director of the FDA's Atlanta District Office.
Still, most passengers don't need to worry about furry pests scurrying about the cabin.
Rodent infestation is not common on planes, said Tamara Ward, an FDA spokeswoman.