BEMIDJI -- Two Burger King restaurants in Bemidji temporarily closed Thursday after more than two dozen people contracted salmonella after eating there.

Doug Schultz, a spokesperson with the Minnesota Department of Health, said the department has confirmed 27 cases, and received reports of four more probable cases.

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Both Burger King sites voluntarily decided to close Thursday.

Most cases were identified in September, he said, but the victims may have been exposed to salmonella before then. Two additional cases came to light this week, prompting the closures.

“They may have been sick a couple weeks or so before then,” Schultz said. “It takes a while before people get symptoms, and then they’re sick enough to go to the doctor, and then we identify.”

Symptoms of salmonella, a bacterial disease that infects the intestinal tract, can include nausea, vomiting, abdominal cramps, diarrhea, fever, chills, headache and blood in the stool, according to the Mayo Clinic.

Once the Department of Health identified the outbreak in September they put “stringent” interventions in place, Schultz said. The Burger Kings were both cleaned and any employees with symptoms were kept from working until they were symptom-free for 72 hours, but the precautions did not stop the outbreak.

“Most of the time that does the trick, 98 percent of the time we don’t see further transmission,” Schultz said. “In this case we had two additional illnesses pop up this week.”

Schultz said the MDH believes the outbreak is due to employee illness, rather than a specific contaminated food item. Before the restaurants can reopen each employee must be tested for salmonella twice.

The earliest the Burger Kings could reopen is next week, according to Schultz. The restaurants must also be thoroughly re-cleaned.

“We do clearly have evidence of food worker illness being part of the problem,” Schultz said.

Attempts to reach the Burger King restaurants for comment were unsuccessful.