Nearly 700 passengers and crew members became ill during a cruise on Royal Caribbean’s Explorer of the Seas. The voyage was cut short and the ship returned to port Wednesday in New Jersey, where it was being sanitized in preparation for its next voyage.  Long lines of weary travelers who arrived to freezing temperatures in Bayonne recalled days of misery holed up in their rooms with extreme stomach cramps, vomiting and diarrhea.

Health investigators suspect norovirus, but lab results are not expected until later this week. The U.S. Centers for Disease Control and Prevention said its latest count puts the number of those sickened at 630 passengers and 54 crew members. The ship, scheduled for a 10-day cruise, was carrying 3,050 passengers.

If norovirus is to blame, it would be one of the largest norovirus outbreaks on a cruise ship in the last 20 years, the CDC said. Norovirus — once known as Norwalk virus — is highly contagious. It can be picked up from an infected person, contaminated food or water or by touching contaminated surfaces. Sometimes mistaken for the stomach flu, the virus causes bouts of vomiting and diarrhea for a few days.

The ship will be sanitized and no one will be allowed aboard for a period of more than 24 hours as an extra precaution, the cruise line said.  “We will perform a thorough ‘barrier’ sanitization program on the entire ship to make certain that any remaining traces of the illness are eliminated,” a Royal Caribbean spokesperson said in an e-mail to FoxNews.com. “It will be the third aggressive sanitizing procedure the ship has undertaken since we became aware of the issue.

Explorer of the Seas is on track to depart at its originally scheduled time Friday afternoon on its next cruise, a nine-night trip with port calls in Puerto Rico, St. Thomas, the Dominican Republic and Haiti, a Royal Caribbean spokeswoman said.