( CNN ) -- Nearly 500 cases of Norovirus have been reported on two Florida-based Princess Cruises ships , the cruise line said Sunday . The 499 cases occurred on the Ruby Princess and the Crown Princess , both based out of Fort Lauderdale , Florida , said cruise line spokeswoman Julie Benson . On Saturday , the Crown Princess returned from a Caribbean cruise with 364 sick passengers and 30 sick crew members , she said . In all , about 3,100 people were on board . Sunday morning , the 3,000 passengers and crew on board the Ruby Princess disembarked , Benson said . Of those on board , 92 passengers and 13 crew members were reported ill. `` We 're working in close cooperation with the CDC to identify the cause , '' Benson said . Investigators with the Centers for Disease Control and Prevention have been on board both vessels and monitoring cleaning procedures , she said . The Crown Princess was cleaned Saturday and has returned to sea , she said . The Ruby Princess was also set to return to sea Sunday afternoon . Passengers on both departing cruises are notified of the outbreak and cleaning , she said , and advised of protective measures . Norovirus causes symptoms including diarrhea , vomiting and stomach pain , according to the CDC . It is spread from person to person through contaminated food or water or by touching contaminated surfaces . CNN 's Dave Alsup contributed to this report .
The fatal illnesses occurred on the Ruby Princess and Emerald Princess . Princess Cruises is working with investigators to determine the cause . Norovirus can cause nausea , vomiting and stomach pains .