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More than 100 people have now reported they got sick with suspected food poisoning at a national Food Safety Summit held earlier this month in Baltimore.

Maryland state health officials say they still don’t know what caused the outbreak of gastroenteritis that left participants suffering symptoms that included diarrhea and nausea.

“We are working on evaluating possible exposures and doing testing at the Maryland state public health laboratory to attempt to identify an agent,” officials said in a letter to attendees.

The conference, held April 8 to 10 at the Baltimore Convention Center, attracted at least 1,300 of the top food safety officials in the nation, including staff from federal agencies such as the Food and Drug Administration and the Centers for Disease Control and Prevention as well as businesses such as McDonald’s, Tyson and ConAgra Foods.

Health officials have heard back from about 400 of those who attended, so the actual toll of illness might be higher.

City health officials inspected the convention center and its food service provider, Centerplate. The company was issued a violation notice for condensation dripping from one of the two ice machines in the kitchen, a spokesman said.