A US food safety summit in Maryland earlier this month has become a cautionary tale after more than 100 attendees came down with suspected food poisoning.
Most of those affected complained of diarrhoea, the Maryland Department of Health and Mental Hygiene said.
Local health officials have heard from about 400 of the 1,300 attendees and are at a loss as to the exact cause of their illness.
The April 8-10 meeting at the Baltimore Convention Centre included representatives from the US Food and Drug Administration and the Centres for Disease Control and Prevention, and food companies such as McDonald's, Tyson Foods and ConAgra Foods.
"We are working on evaluating possible exposures and doing testing at the Maryland state public health laboratory to attempt to identify an agent," the health department said.
The convention centre and its food service provider, Centreplate, were inspected by city health officials.
Centreplate was issued a violation notice for condensation dripping from an ice machine in the kitchen, according to NBC News.
Centreplate declined a request for comment.