(CNN) -- The Centers for Disease Control is making a no-sail recommendation for at least four full days for the Celebrity Mercury cruise ship to investigate recurring outbreaks of gastrointestinal illness, a CDC spokesman said Monday.
"The CDC and the cruise line corporate staff have not yet determined why the controls that they were following have not been effective," said CDC spokesman Ricardo Beato.
Celebrity Cruises has been notified of the no-sail recommendation, Beato said.
Members of the CDC's Vessel Sanitation Program, which works with the cruise industry to prevent and control gastrointestinal illnesses, were on the ship Monday looking for causes of the latest wave of illness, which is the third outbreak on the ship since mid-February. Norovirus, which causes vomiting and diarrhea, was identified as the source of the first two outbreaks, according to Beato.
VSP personnel inspected the ship after the first outbreak in February, which sickened more than 20 percent of passengers, and made recommendations to prevent further outbreaks. The ship's next sailing was delayed by a day for a full cleaning.
Despite those measures, about 10 percent of passengers on the next sailing became ill with norovirus. About 19 percent of passengers have become ill on the latest sailing, which has prompted Celebrity to cut the cruise short by a day, skipping a stop Monday in Tortola, British Virgin Islands, Celebrity Cruises said in a statement.
The Mercury will return to Charleston, South Carolina, on Thursday morning. Passengers have been compensated for the interrupted itinerary, said Celebrity Cruises spokeswoman Cynthia Martinez.
"Guests currently onboard Celebrity Mercury received an onboard credit in the amount of one day of the cruise fare paid for their sailing, as well as a future cruise certificate for 25 percent of the cruise fare paid," she said in an e-mail.
The latest outbreak is the ninth incidence of gastrointestinal illness reported to the VSP this year affecting more than 2 percent of passengers on a cruise ship.
A high incidence of norovirus in many parts of the world this year is likely to translate to cruise ships, according to Capt. Jaret Ames, branch chief of the VSP.