Princess Cruises confirmed that one of its cruise liners, the Ruby Princess, reported a COVID-19 outbreak before docking in San Francisco.

The cruise operator requires passengers and crew members to be fully vaccinated for COVID-19, which is caused by the CCP (Chinese Communist Party) virus. Princess Cruises also mandates passengers to show a negative COVID-19 test and proof of vaccination to board, according to its website.

Those who tested positive were “isolated and quarantined while monitored and cared for by our shipboard medical team,” Princess Cruises said in a statement to news outlets Monday. It did not say how many people tested positive or when they tested positive during the cruise.

“They were all asymptomatic or only mildly symptomatic,” the firm said. Some of the passengers who contracted the CCP virus did not finish their quarantine and were either sent home or “were provided with accommodations ashore to hotels coordinated in advance for isolation and quarantine,” the statement added.

“As with all Princess itineraries, this cruise is operated as a vaccinated cruise, as defined by the U.S. Centers for Disease Control and Prevention,” the company told the San Francisco Chronicle. “Guests and crew vaccination rates were at 100 percent.”

The Ruby Princess docked in San Francisco on Sunday, the company said, after the ship was on a 15-day cruise to the Panama Canal. The ship departed later that day on a 15-day cruise to Hawaii, said Negin Kamali, spokesperson for Princess Cruises, in a statement to USA Today.

Under the Center for Disease Control and Prevention’s (CDC) cruise ship monitoring website, the Ruby Princess is described as “under observation” by the federal health agency.

The development comes about two weeks after the CDC lowered its COVID-19 warning for cruise travel to “Level 2,” a “moderate” risk. Previously, the agency gave cruise travel a “Level 4” warning, which is the highest level, as the Omicron variant spread across the United States several months ago.

During the COVID-19 pandemic, the cruise industry has been battered by lockdowns and federal restrictions on cruises—amid early speculation that cruise ships were “super spreaders” of the virus. Industry data suggests that cruise companies collectively lost $63 billion in 2020 and 2021.

On March 18, the CDC released new COVID-19 guidelines for the cruise industry, with a spokesman telling USA Today that it entails the agency’s suggestions on social distancing, quarantine requirements, and port agreements.

The Epoch Times has contacted Princess Cruises for comment.