(AP) — The number of confirmed cases of a rare food-borne illness in Nebraska has climbed to 23 as state and federal public health agencies try to figure out where it’s coming from.

An outbreak of cyclosporiasis (cyclo spoh RYE uh sis) is confined mostly to eastern Nebraska and could be linked to Iowa where 45 people were confirmed sick as of Friday.

Iowa’s public health medical director Dr. Patricia Quinlisk says fresh vegetables may be the culprit but the investigation continues.

Consumers should wash fruits and vegetables to reduce the risk of getting the illness, which causes diarrhea lasting an average of 57 days. It’s caused by a parasite carried in human feces that contaminates food.

The illness is rare in Nebraska. No cases were reported in the last four years.