Walt Disney Co’s cruise division said on Monday it had postponed its first test cruise since the onset of the pandemic after a few volunteers showed inconsistent COVID-19 test results.

Several cruise lines have planned to resume voyages from the United States after many months, with Royal Caribbean Group’s Celebrity Edge last weekend becoming the first vessel from a major operator to sail from a U.S. port.

The Disney Dream ship was scheduled to set sail with about 300 volunteers on Tuesday, but the cruise was cancelled as a small number of employees showed inconsistent COVID-19 test results that were considered positive by the U.S. Centers for Disease Control and Prevention.

Disney Cruise Line did not say when it would next commence sailing of the ship.

Royal Caribbean executive Michael Bayley last week said two unvaccinated teenagers had tested positive on its Adventure of the Seas ship, adding that 92% of guests were fully vaccinated.