A health official says food poisoning perhaps from an ingredient in chicken salad could be what killed three Louisiana mental health hospital patients and sickened 40 others.

Officials say patients at Pineville’s Central State Hospital showed signs of gastrointestinal stress beginning Friday morning. The three deaths — a 43-year-old woman, 41-year-old man and 52-year-old man — happened late Friday night or early Saturday morning.

Lisa Faust, a spokeswoman for the state Department of Health and Hospitals, says the patients had chicken salad Thursday night.

She says something bad could have been in the chicken, lettuce or mayonnaise.

Officials say the poisoning appears to be isolated to the hospital in Pineville, located between Shreveport and Baton Rouge.