US health officials on Sunday boarded a cruise ship docked in the Virgin Islands to investigate an illness outbreak.
At least 300 people have been stricking with gastrointestinal symptoms including vomiting and diarrhea.
The US Centers for Disease Control and Prevention has said almost 10% of the 3,000 or so passengers aboard Royal Caribbean International's Explorer of the Seas have reported getting sick during a Caribbean cruise that left Cape Liberty, New Jersey, on Tuesday. 22 crew members are also sick.
At least two CDC officials, an epidemiologist and an environmental health officer, were expected to do the investigation and evaluate the outbreak response on the cruise liner. The health agency did not immediately respond to a Sunday email and a call seeking comment about the work aboard the ship.
During the previous port call in Puerto Rico, the ship underwent "extensive and thorough sanitizing" to help prevent more people from getting sick, said Royal Caribbean spokeswoman Janet Diaz. It bypassed a scheduled stop to the company's fenced-in beach destination in northern Haiti to sail directly to Puerto Rico's capital.
Meanwhile, the passengers and crew who fell ill have "responded well to over-the-counter medication being administered onboard the ship", she said.
Fast-spreading norovirus is often to blame for similar symptoms sweeping closed quarters like those on cruise ships, but a determination will likely have to wait until samples are tested in a lab. Symptoms of norovirus include vomiting and diarrhea. Diaz said special cleaning products and disinfectants proven to kill norovirus are being used to clean the ship.