American woman vanishes while on vacation in Belize

An American woman disappeared over the weekend while vacationing in Belize, authorities said.

Alison MacKenzie, 43, of Arizona, was among a group of tourists who on Friday embarked on an overnight excursion to Rendezvous Caye, a tiny island off the coast of Belize. A member of the tour group reported that when they woke up the next morning around 6:00 a.m., MacKenzie was nowhere to be found, according to a spokesperson for the Belize Police Department.

The police spokesperson told ABC News that the investigation is ongoing and nothing has been ruled out. As of Tuesday night, a person-of-interest had not been identified and no one had been detained for questioning.

An official with the U.S. Department of State told ABC News in a statement, "We are aware of reports of a U.S. citizen missing in Rendezvous Caye, Belize."

"Whenever a U.S. citizen is missing, we work closely with local authorities as they carry out their search efforts, and we share information with their family however we can," the official said. "Due to privacy considerations, we have no further comment at this time."

ABC News' Christine Theodorou contributed to this report.