An American passenger aboard a cruise touring the Caribbean islands was reported missing when she failed to return to the vessel after an excursion in Sint Maarten last Thursday, local officials said.

Ann Evans, 55, embarked on the Holland America Line’s 12-day cruise in the Caribbean on Nov. 16. Just four days in, she mysteriously vanished during an “organized island tour” of Sint Maarten, according to a missing person alert from the Government of Sint Maarten.

Evans left the “Rotterdam” ship around 10 a.m. that morning and boarded a bus for the tour, but officials said she “did not return to the bus or to the cruise vessel.”

The missing person alert was posted on Nov. 26. It’s unclear exactly when Evans’ disappearance was officially reported.

Sint Maarten, the southern part of the island, is technically part of the Netherlands, while the northern Saint Martin is controlled by France. Both respective law enforcement agencies are working in tandem to locate Evans, according to the release.

Their stop in Sint Maarten was just the second of seven during the pricey $1,000 journey, according to CruiseMapper. The day before, passengers lounged on the beaches at Half Moon Cay, RelaxAway, which is a Bahamian island owned by the Carnival Cruise Line.

The “Rotterdam” is the newest ship in Holland America Line’s fleet, according to its website. It can house upwards of 2,600 passengers at double occupancy, or up to 4,173 guests when its 197 staterooms are fully booked.

It’s unclear if Evans was traveling with anyone or boarded the cruise solo.

Holland America assured that it “notified local authorities immediately” and is “working closely with them to confirm the guest’s whereabouts,” according to a statement obtained by The Post.

The “Rotterdam” departed from Puerto Rico yesterday and is set to return to Fort Lauderdale on Nov. 28.