Visitors to this year's Royal Welsh show are being warned to check for symptoms of bacterial infection after unpasteurised cow's milk was distributed at the show.
The milk produced at Penlan y Môr Farm near New Quay has been linked with four cases of Campylobacter.
Public Health Wales, Hywel Dda University Health Board, the Food Standards Agency and Ceredigion County Council are currently investigating.
Symptoms of Campylobacter infection include persistent nausea, diarrhoea, stomach cramps, and fever.
People with weakened immune systems are particularly vulnerable to food poisoning, and are advised not to consume unpasteurised milk or cream. Vulnerable groups include pregnant women, infants, children and older people.