(The Hill) — Morel mushrooms have been linked to a deadly outbreak in Montana last year, a study in the Center for Disease Control’s Morbidity and Mortality Weekly Report said Thursday.

According to the study, between March and April of last year, 51 people reported “mild to severe gastrointestinal illness” in the wake of eating at a restaurant in Bozeman, Montana. Three people were hospitalized and two people died. 

Following an inspection and the temporary closure of the restaurant, the Montana Department of Public Health and Human Services and Montana’s Gallatin City-County Health Department “collaborated with CDC to conduct a matched case-control study among restaurant patrons to help identify the source of the outbreak,” according to the study. 

“Consumption of morel mushrooms, which are generally considered edible, was strongly associated with gastrointestinal illness,” the study reads. “A dose-response relationship was identified, and consumption of raw morel mushrooms was more strongly associated with illness than was consumption of those that were at least partially cooked.”

After the outbreak, public service announcements were made regarding the consumption of morel mushrooms, the study said.

It also said the “investigation highlights the importance of prompt cross-agency communication and collaboration, the utility of epidemiologic studies in foodborne disease outbreak investigations, and the need for additional research about the impact of morel mushroom consumption on human health.”

“Although the toxins in morel mushrooms that might cause illness are not fully understood, proper preparation procedures, including thorough cooking, might help to limit adverse health effects,” the study continued.