Health officials say the likely source of the botulism outbreak that killed one person and sickened many others at an Ohio church potluck dinner was home-canned potatoes used in a potato salad.

The Ohio Department of Health said Monday that testing has narrowed the source to potato salad served at the April 19 potluck at Cross Pointe Free Will Baptist Church in Lancaster, which is southeast of Columbus.

A 55-year-old woman died, and officials have confirmed 20 other botulism cases, along with 10 suspected cases. A dozen people are still in the hospital. Patients have been treated with a botulism antitoxin provided by the Centers for Disease Control and Prevention.

Botulism is a rare but serious illness caused by a nerve toxin that is produced by certain kinds of bacteria.