One of the largest cruise ships in the world, Royal Caribbean’s Oasis of the Sea, returns early to Port Canaveral, Florida after a norovirus outbreak affected more than 100 passengers on Thursday.

The Royal Caribbean cruise ship which departed from Port Canaveral, Florida on Jan 6. was scheduled for seven days and carried 9,000 passengers, including guests and crew members on Sunday.  It’s itinerary showed stops in Haiti, Jamaica, and Mexico. Guest and crew members began getting sick when it made its first stop in Haiti on Tuesday where the ship hosted a lunch buffet on land, according to Abby Perrin, a passenger on the ship. Perrin claimed that she and her mother began experiencing symptoms associated with food poisoning such as vomiting that night.

The ship then arrived to Jamaica and other passengers reportedly started feeling symptoms. Passengers said they were not allowed to leave the vessel. On Thursday morning, the ship headed to Conzumel, Mexico, but officials canceled the cruise while it was still in route.

The number of sickened guests and passengers had increased to nearly 500 people since then.

Officials said the Centers for Disease Control and Prevention is investigating. They said norovirus is the leading cause of foodborne illness in the U.S., with most instances of norovirus occurring in public places like restaurants.

Norovirus is typically the most common cause of foodborne diarrhea and includes stomach-gripping symptoms such as diarrhea and nausea and is “very contagious.” You can catch it from people infected by it and by touching contaminated surfaces or eating or drinking contaminated food and water

“All of the ship’s guests will receive full refunds of their cruise fare paid,” said Owen Torres, spokesperson for Royal Caribbean. “We think the right thing to do is to get everyone home early rather than have guests worry about their health.” In a somewhat unusual move, the cruise line has decided to provide travelers with full refunds of their paid cruise fares.