MANKATO — Health officials have traced the source of a norovirus outbreak in Mankato to an ill or recently ill food service worker or workers.

Dozens of people who ate at Mankato civic center events were sickened this month.

A Minnesota Department of Health spokesman said an investigation narrowed the outbreak to the food service provider.

Health department spokesman Doug Schultz said it won’t be possible to trace the source of the norovirus to a particular person.

Schultz said following the outbreak, health officials conducted an “intervention” with the food service provider that included reminders of what to do when employees become ill.

Messages left for the catering business owner were not immediately returned Wednesday.

Norovirus causes vomiting or diarrhea. Most people recover in one or two days.