One person has died and at least 20 others were sick with symptoms of botulism following a weekend church potluck in Ohio, hospital officials said on Tuesday.

The Fairfield Medical Center said in a statement that the patients, five of whom were in a critical condition, had all attended a picnic at Cross Pointe Free Will Baptist Church in Lancaster on Sunday.

The US Centers for Disease Control and Prevention (CDC) had sent anti-toxin to treat the sick, the hospital said, while local health officials investigated the cause of the outbreak.

The church's pastor, Rev Bill Pitts, said the lunch was similar to others held there.

"Everyone is trying to find the common thread," he said. "My heart is crying and I pray for the people and their families."

Botulism is a rare but potentially fatal paralytic illness caused by a nerve toxin that is produced by certain bacteria, according to the CDC.

Symptoms include drooping eyelids, slurred speech and muscle weakness, which can progress to paralysis of the limbs and respiratory muscles.

The hospital said botulism is not contagious, so there is no threat to the public at large or people at the hospital. Symptoms generally begin showing up within 36 hours of eating the contaminated food, but can start as many as 10 days after, the hospital said. Around 60 people attended the supper and the hospital advised them all to seek medical attention even if they were free of symptoms.

Additional reporting by Reuters.