Health inspectors on the Caribbean island of Curacao boarded a Scientology cruise ship early Saturday to investigate a reported case of measles, a source familiar with the situation told ABC News.

Freewinds, which belongs to the Church of Scientology, was quarantined in St. Lucia earlier this week after it was discovered that someone aboard the ship had measles. It arrived its home port of Willemstad on the Dutch Island around 6:00 a.m. local time on Saturday, according to the Curacao Ports Authority.

"Health inspectors are on board and interviewing everybody according to international rules. Everybody must [have] proof they are vaccinated. This, of course, is a challenge being on a cruise ship. But because [the] Curacao team was in contact with [the] ship since the beginning of this week pax [passengers] and crew already had time to prepare to locate those documents via family, et cetera," the source said.

"It seems, for now, that only one case was there from the beginning and did not spread due to good precautions by the ship," the source said.

On Tuesday, Dr. Merlene Fredericks-James, the chief medical officer in St. Lucia, announced that a cruise ship that had docked on the island was being quarantined, as health officials investigated a possible case of measles on board. By Wednesday, St. Lucia police confirmed the ship in question was the Freewinds, and that it belonged to the Church of Scientology.

There are about 300 crew members and passengers on board, Albert Elens, managing director of Maduro Shipping, the Freewinds' agent in Curacao, told ABC News earlier this week.

ABC News' Ben Gittleson contributed to this report.