Three people in a meatpacking plant with nearly 800 employees have been diagnosed with salmonella. The plant has remained open, and although officials have not determined the source, they say all three people ate in the cafeteria.

The source of the outbreak is not known, and further testing is required. A representative of Hormel Foods, parent company of Rochelle Foods Inc., said the plant did not have to be closed and none of the meat was contaminated. Hormel spokeswoman Julie H. Craven said the company started to hear about the salmonella problem last week.

Two of the confirmed cases are employees and the other is an associate of the plant. O’Brien said the company has been cooperative, as has C.L. Swanson Corp., which contracts the cafeteria service at the plant. The three people with confirmed cases were found to have eaten breakfast in the cafeteria.