Health Officials on the island of Curacao boarded the Church of Scientology ship quarantined over an outbreak of measles on Saturday. The ship arrived at the island in order for officials to begin vaccinating people onboard. Officials said only those who already have been vaccinated or have previously had measles will be free to leave the ship titled Freewinds. Curacao epidemiologist Dr. Izzy Gerstenbluth told The Associated Press that a small team is assessing more than 300 people onboard, and that the process could take more than a day. “We will go on board and do our job,” Gerstenbluth said. “... This is what happens when we don’t vaccinate.”

Authorities believe the people onboard might have been exposed after a female crew member was diagnosed with measles after coming back from Europe. Gerstenbluth said the crew member arrived in Curacao April 17 and visited a doctor April 22 with cold symptoms. A blood sample was taken, confirming it was measles—a day after the ship had departed for St. Lucia. Freewinds was then put under quarantine in St. Lucia, before it returned to its home port of Curacao on Saturday.