Updated

A cruise line says about 350 people are responding well to medicine after getting sick on a cruise to the Caribbean that departed from South Carolina.

Celebrity Cruise spokeswoman Cynthia Martinez said Tuesday that 326 of the more than 1,800 passengers on the Celebrity Mercury began complaining Sunday of upset stomachs, vomiting and diarrhea. Martinez says 27 of the nearly 850 crew members also reported symptoms.

The ship left Charleston on Feb. 15.

Martinez says the crew is conducting "enhanced cleaning" to prevent the spread of the illness.

An extra doctor and two nurses came aboard in St. Kitts in the British Virgin Islands and will sail to Charleston, arriving Friday.

It's not clear what pathogen was involved, but samples were being dropped off in Puerto Rico for testing.