About 100 people who attended an April 20 fundraiser at the Hilton in Rye Brook complained of stomach ailments. Another 200 people reported illness after attending a sorority brunch last weekend.
The Health Department says hotel managers have been "extremely cooperative" in implementing its recommendations.
Banquet and kitchen staff have been placed on a 72-hour, paid furlough. Food preparation procedures have been changed as a precaution.
The hotel said it was "fully cooperating" with the department to make sure the cause of the illness is found and the situation dealt with quickly.
Norovirus is highly contagious and often spreads in places like schools, cruise ships and nursing homes.