The Cincinnati Health Department has said that it is OK to eat again at the Hilton Netherland Plaza hotel in downtown Cincinnati, but that they will continue to investigate a recent outbreak of food poisoning there.

Up to 1,500 people from the Cincinnati area, as well as Ohio and 12 other states, attended 16 catered events or conventions at the hotel between Nov. 29 and Dec. 3.

As many as one-third of them may have become ill with food poisoning. The department tested stool samples from some of the victims and found no common bacterial causes of food poisoning such as salmonella, shigella and E. coli.

The samples did test positive for norovirus, the most common food-borne illness in the country, accounting for about half of all cases, the health department said.