A Carnival Cruise Line ship that left from Galveston, Tex., has 27 coronavirus-positive people on board, according to the Belize Tourism Board. The outbreak is among the highest number of publicly reported cases on a ship sailing from the United States since cruises restarted this summer.

According to the statement from Belize tourism officials, 26 of the infected people are crew members and one is a guest. All are vaccinated, and most have either mild or no symptoms.

The ship is continuing to sail and arrived in Cozumel on Thursday.

In an email, Carnival spokesman Chris Chiames said the crew members “remain in quarantine and/or isolation on board.” He said the line has made multiple announcements to guests on the ship and had already disclosed that there were positive cases last week.

Following that disclosure, the company put new mask rules into place for some indoor areas of all its ships effective last weekend. That policy went into place early, the night of Aug. 4, on Carnival Vista.

The company also added a requirement that passengers — regardless of their vaccination status — must show proof of a negative coronavirus test taken within three days of boarding, effective this coming Saturday.

But last week’s statement from Carnival said only that the cruise line was “managing a small number of positive cases on board.” The company would not say how many at the time, and it did not answer a follow-up question over the weekend. A statement from Carnival on Thursday echoed that language.

“Carnival Vista is managing a small number of positive covid cases that surfaced on the cruise that returned to Galveston last Saturday, despite all our crew and almost all of our guests being vaccinated,” the statement says. “Several announcements have been made to guests currently on board to keep them updated.”

The number of people with positive test results was not publicly released until Wednesday’s news release from Belize. The statement said the ship had 2,895 passengers — 96.5 percent of whom are vaccinated against the coronavirus — and 1,441 crew, 99.98 percent of whom are vaccinated.

Officials in Belize met virtually with ship officials on Tuesday, the day before Vista was set to arrive.

“The team at Carnival noted that all positive cases have been isolated and contact tracing has ended with no additional positive cases found, and that the infected crew and passenger do not pose a threat to guests, crew or frontline workers in Belize,” the statement said.

Passengers were allowed to leave the ship in Belize on Wednesday, but those with negative tests were asked to show proof, and those without were subject to random testing. The tourism board said that passengers would not be allowed to leave the ship if the number of positive cases exceeded 2 percent of the total number of passengers.

Carnival said in its statement that close contacts of those who tested positive were placed in quarantine. All unvaccinated passengers who left the ship on Saturday were tested, according to company protocols, and none were positive.

The cruise line said it randomly tests “a large percentage of our crew on a rotating basis multiple days per week — including more than 900 over the last seven days.”

Carnival said it is in daily contact with the Centers for Disease Control and Prevention about the status of all its ships and was cleared to sail on Saturday.

The CDC does not release information about the number of positive cases on cruise ships. On its website showing the covid-19 situation on ships sailing from the United States, the agency has Carnival Vista at “yellow” status, which means cases have been reported in the past seven days and the ship has met the threshold for an investigation. The vessel “remains under observation,” the site says.

Carnival requires passengers and crew on its ships to be vaccinated, although some passengers — including children too young for the authorized vaccines and those with medical issues — are allowed to request exemptions ahead of time. It is committed to sailing with at least 95 percent of passengers vaccinated in compliance with CDC rules for how cruise lines can restart after the industry shut down in March 2020.

Carnival Vista was the first ship to start sailing again for Carnival, on July 3.

In Thursday’s morning announcements shared by Carnival, the captain thanked everyone who was randomly tested in Belize. He said 68 passengers had been tested and all were negative.

“We are dedicated to your health and safety and appreciate your cooperation with all of our onboard procedures,” he said.