Twenty-seven vaccinated people who are on board the Carnival Vista cruise ship tested positive for COVID-19, according to the Belize Tourism Board.

Twenty-six of the positive cases are among Carnival crew members, with only one passenger testing positive. According to the tourism board, everyone who tested positive was vaccinated and “most are asymptomatic or have very mild symptoms.”

The ship departed from Galveston, Texas, and was headed to Belize when the outbreak was reported to authorities.

Last week the cruise line reported some positive cases on the Vista, but it would not disclose the number.

“We have managed the situation utilizing stringent health protocols which included placing those who tested positive in isolation and close contacts in quarantine,” Carnival said in a statement on Friday to ABC News. “Guests on board the July 31 and August 7 sailings were notified and kept updated, and the CDC and destination officials have been apprised.”

Contact tracing was initiated for the other almost 3,000 guests and 1,500 crew on board the ship, which docked in Belize on Wednesday.

The country’s tourism board says “no further cases have been found,” and the ship continued its sailing, docking in Cozumel yesterday.

“After a thorough review of the situation, and after determining that the risk is low, including the fact that CDC is aware of the situation, it was concluded that the situation is contained, and safety protocols are proving effective,” the board added.

The outbreak on the ship is among the worst since cruises resumed sailing this summer.

In response, Carnival updated its mask policy last week, requiring all guests on the Vista to wear masks in some indoor areas. Beginning tomorrow on all Carnival sailings, guests will also be required to show proof of a negative COVID-19 test in order to sail — regardless of their vaccination status.

Guests are scheduled to disembark tomorrow and the cruise line says all unvaccinated guests will be tested today before arriving in the U.S.

“The CDC’s conditional sail order and our own protocols anticipate the potential for COVID on board,” Carnival said, “and our procedures are designed to manage and mitigate any situation.”