More than 600 people aboard a cruise ship in the Caribbean have become violently ill, forcing the ship to cut its cruise short and reverse course back to the United States.

The first case of illness on Royal Caribbean’s Explorer of the Seas was reported less than 24 hours after the ship left New Jersey last Tuesday.

Officials have yet to determine what’s caused the illness, but Royal Caribbean says the symptoms resemble norovirus, which causes nausea, vomiting and diarrhea. Norovirus was responsible for widespread illness on seven cruise ships last year.

Officials with the U.S. Centers for Disease Control and Prevention boarded the Explorer of the Seas Sunday as it was docked at a port in U.S. Virgin Islands. The ship is currently on its way back to the United States, cutting its 10-day itinerary short by two days.

Arnee Dodd, a passenger who caught the sickness, told CTV Toronto in a phone interview from the ship that “it almost had no warning. Just high fever, chills, aches, dehydration.”

Jordan Nobel, a Canadian passenger on the cruise, said that crews have been vigorously scrubbing the ship in an effort to sanitize it,

“I’ve seen many, many different staff members wiping down all the walls, wiping down every chair on the deck of the boat, that sort of thing,” he said. “I’ve been very impressed,”

Audio recordings of a captain’s briefing, however, reveals that some passengers on the ship have been frustrated with the response to the outbreak and some crewmembers’ cavalier attitude to the situation. On the recordings, which were obtained by CTV News, the captain of the Explorer of the Seas can be heard trying to quell passengers’ anger.

“This is totally our problem. It is completely our problem. You are our guest in our home, if you like. We are responsible,” he said.

Royal Caribbean said in a statement that it felt heading back to the United States was its best option,

“We think the right thing to do is to bring our guest home early and use the use the extra time to sanitize the ship even more thoroughly,” the statement said. The cruise company said it is expecting to see more cases of the illness. It says it also plans to compensate passengers with a full refund as well as hotel and airfare in New Jersey. The ship is expected to arrive in New Jersey on Wednesday.

Earlier in the month, 70 passengers aboard another Royal Caribbean cruise ship fell ill due to a suspected outbreak of norovirus.

With a report from CTV Toronto’s Colin D’Mello and The Associated Press