Raleigh, N.C. — State public health officials on Tuesday linked illnesses among scores of students at a leadership conference in Raleigh last month to a banquet at the Raleigh Convention Center.

About 150 of the 1,000 students from across the state who gathered at the downtown Raleigh Sheraton for a YMCA Youth & Government meeting on Feb. 12-14 reported nausea, vomiting and diarrhea. Five were taken to area hospitals.

Wake County and state public health officials conducted an intensive investigation to determine the source of the illnesses, including surveying more than half of the conference attendees. Investigators found that students who ate at a Feb. 12 banquet at the convention center were almost three times more likely to get sick as those who didn't attend the banquet. No other meals were associated with illness, officials said.

Initial tests cited norovirus as the cause of the illnesses, but officials said follow-up tests couldn't confirm that. Noroviruses cause symptoms of intestinal distress and can spread quickly in confined spaces.

“The timing of the outbreak and the fact that most sick attendees had only diarrhea and not vomiting make it unlikely that norovirus was the main cause of the outbreak,” Dr. Megan Davies, state epidemiologist, said in a statement. “Still, some students might have had norovirus when they arrived at the conference in Raleigh.”

The short time between the dinner and the onset of illness makes it more likely that bacterial toxins, a common cause of food poisoning, were to blame, officials said. The Centers for Disease Control and Prevention is conducting tests to pinpoint the toxin that caused the illnesses.

Bacterial toxins typically cause diarrhea, stomach cramps or vomiting within a few hours of eating contaminated food. The keys to preventing food-borne illness caused by these toxins are thoroughly washing raw ingredients to reduce bacteria on the food; keeping cooked foods separate from raw, uncooked foods; thoroughly cooking meat and poultry; and keeping cooked foods at safe temperatures after cooking.

Convention Center Director Roger Krupa said Tuesday evening that he doesn't believe the findings of the state investigation but said he and his staff would continue to review it.

"At this point, it's hard to accept the report," Krupa said. "All of the evidence is statistical and circumstantial. There are no lab results, no food samples, nothing factual."

The kitchens at the convention center and Sheraton were sanitized immediately after the illness outbreak, and Wake County health officials cleared the convention center to continue serving meals.