The Royal Caribbean International's Explorer of the Seas is docked at Charlotte Amalie Harbor in St. Thomas, U. S. Virgin Islands, Sunday, Jan. 26, 2014. U.S. health officials have boarded the cruise liner to investigate an illness outbreak that has stricken at least 300 people with gastrointestinal symptoms including vomiting and diarrhea. AP Photo/Thomas Layer BAYONNE, N.J. (AP) - The number of passengers and crew reported stricken ill on a cruise ship returning to New Jersey has risen to nearly 700. The U.S. Centers for Disease Control and Prevention said Wednesday its latest count puts the number of those sickened aboard the Explorer of the Seas at 630 passengers and 54 crew members. Royal Caribbean says most guests who fell ill are now up and about as the ship heads to port in Bayonne, where it is scheduled to dock Wednesday afternoon. The CDC is recommending that people who still have symptoms be housed in nearby hotels or seen at medical facilities. Health investigators suspect a norovirus is to blame. If it is, the CDC says it would be one of the worst cruise ship norovirus outbreaks in 20 years. A cruise ship on which hundreds of passengers and crew members fell ill was due to return Wednesday to the New Jersey port from which it departed last week, scheduled for another sanitation procedure before heading out in two days for its next planned trip. Royal Caribbean said the Explorer of the Seas was set to dock at 2 p.m. in Bayonne, a city near New York Harbor. The ship had to cut short a 10-day cruise after more than 600 passengers and crew members experienced vomiting and diarrhea. The cruise line said most guests who fell ill were up and about as the ship headed to port. The U.S. Centers for Disease Control and Prevention boarded the ship during its U.S. Virgin Islands port call but hasn't confirmed the cause of the outbreak. According to the CDC, 577 out of 3,050 passengers reported being ill. Forty-nine crew members also got sick. The ship's doctors said the symptoms were consistent with norovirus. Royal Caribbean is providing all guests a 50 percent refund of their cruise fares and an additional 50 percent future cruise credit. It's also reimbursing airline change fees and accommodations for guests who had to change plans for traveling home. Stricken guests who were confined to their staterooms are also being provided a credit of one future cruise day for each day of confinement. After returning to port, the ship will undergo a third sanitation and no one will be allowed aboard for a period of more than 24 hours as an extra precaution, the cruise line said. Explorer of the Seas is on track to depart at its originally scheduled time Friday afternoon on its next cruise, a 9-night trip with port calls in Puerto Rico, St. Thomas, Dominican Republic and Haiti, a Royal Caribbean spokeswoman said.