Dr. Paul Cieslak, communicable disease manager at the Oregon Department of Human Services, said lab results will not be back for a few days.
Those stricken ate at the Si Las Flores restaurant Jan. 6-8. Health officials say there is no longer a risk in eating there.
Cieslak said Oregon typically sees about 100 cases a year and that it is the most common form of food-borne illness.
"Usually it's from a sick human who has diarrhea, doesn't wash their hands and prepares some food and gets the virus into the food," Cieslak said. "There's always a possibility food came into the restaurant contaminated. We never did identify which food it was..."
Norwalk's symptoms begin 24 to 48 hours after ingestion and typically last a day, Cieslak said. There is no long-term risk.
Symptoms include intense vomiting and diarrhea, Cieslak said