Federal inspectors on Wednesday suspended processing at a poultry plant in California found to have been infested with cockroaches four times over the past five months.
The Foster Farm plant is one of three in central California being investigated for an outbreak of antibiotic-resistant salmonella.
The ongoing outbreak has sickened 416 people in 23 states according to the federal Centers for Disease Control and Prevention in Atlanta.
In October, the U.S. Department of Agriculture refused to close the Livingston, Calif. plant, saying Foster Farms had "submitted and implemented immediate substantive changes to their slaughter and processing to allow for continued operations."
On Dec. 18, Dan Englejohn, assistant administrator of the USDA's Office of Field Operations, told USA TODAY that Foster Farms had proven to the agency that the company was taking steps to control contamination at the plants.
He said the USDA continued "to be very much involved in making sure the facilities are implementing the corrective actions."
However according to the letter sent to Foster Farms CEO Ron Foster on Wednesday, USDA Food Safety Inspection Service staff documented four cases of live cockroach contamination in the plant, on Sept. 14, Nov. 4, Dec. 28 and finally on Jan. 7. The letter was first reported by The Oregonian newspaper.
"These recent findings of egregious insanitary conditions related to a cockroach infestation in your facility indicate that your establishment is not being operated and maintained in sanitary conditions," the letter said.
In a statement provided by spokeswoman Karmina Zafiro, Foster Farms said it was first notified of the infestations on Jan. 8 and "closed the Livingston facility immediately for sanitization and treatment."
No other Foster Farms facilities were affected, according to the statement. "No products are affected. Product production has been transferred to the company's other facilities."
Foster Farms is the nation's sixth-largest chicken processor. Chicken is the most consumed meat in the United States. Americans ate 83 pounds per person in 2013 according to the USDA.
The USDA has removed its inspectors from the plant. Under federal law, slaughterhouses and meat processing plants cannot operate without inspectors on site, so the removal effectively closes the plant.
Cockroaches have been documented carrying viruses and bacteria, including salmonella.
Some food-safety experts wondered why the plant hadn't been shut down earlier as people have been falling ill since October.
"It's probably that USDA was getting bad PR so it needed a reason to shut them down. Cockroaches are never good; but neither are 416 sick people," said Doug Powell, a food-safety expert based in Australia.
Finding roaches in a processing plant isn't unexpected, said Donald Schaffner, a professor of food science at Rutgers University in New Brunswick, N.J. "The key question is how many other plants have this frequency of roach non-compliance and were not shut down?"
Seattle food-safety lawyer Bill Marler found it odd that the USDA "has the power to shut a plant down when they found cockroaches but doesn't have the power to shut them down when they poison hundreds of people with antibiotic-resistant salmonella."
Michael Winter & Elizabeth Weise, USA TODAY