Two people tested positive while on a fully vaccinated Celebrity Millennium cruise, according to a Royal Caribbean Group news release.
The two people are asymptomatic and are isolating in their stateroom onboard the ship. The two found out they were positive after undergoing a required end-of-cruise testing, the company said.
"We are conducting contact tracing, expediting testing for all close contacts and closely monitoring the situation," the Royal Caribbean Group said.
Prior to embarking on the voyage from St. Maarten on June 5, Celebrity Millennium confirmed it required all passengers and crew to provide proof of a negative COVID-19 test within 72 hours and show proof of vaccination.
FILE - Star Princess and Celebrity Millennium cruises docked at the South Franklin dock, Juneau, Alaska.
"This situation demonstrates that our rigorous health and safety protocols work to protect our crew, guests and the communities we visit," the company said.
Celebrity Cruises became the first major cruise ship to set sail with U.S. passengers more than a year after the industry was anchored during COVID-19.
The Celebrity Millennium embarked on a seven-day cruise visiting Aruba, Barbados and Curacao with about 500 passengers and more than 95% of those fully vaccinated, including all crew members. Those traveling with children unable to get their shots were mandated to present a negative COVID-19 test.
The U.S. Centers for Disease Control and Prevention implemented strict health and safety guidelines for cruise lines to resume sailing in U.S. waters. Operators must conduct mock test cruises simulating the real excursion and demonstrating they can comply with requirements or demonstrate that 98% of crew members and 95% of passengers are fully vaccinated.
FOX News contributed to this report.