State health officials are looking for the source of an illness that struck at least 50 people who attended a community picnic in Middle Tennessee.

The St. Patrick's Irish Picnic in McEwen is a 158-year tradition that brings in about 20,000 people annually.
Department of Health spokeswoman Shelly Walker told WTVF-TV  reports started coming in a few days after this year's event on July 27-28. Walker said a few cases have tested positive for a strain of salmonella bacteria. She said investigators have also interviewed a number of people who attended the picnic and did not become ill.

Various food items have been tested, but the department has not isolated the source of the illness.