(CNN) A 36-year-old US citizen has been reported missing in Costa Rica, according to the country's Judicial Investigation Department.

Carla Stefaniak was last seen in a suburb outside the capital of San Jose, authorities said.

The last time anyone heard from Stefaniak was the night of November 27, according to police. Stefaniak and her sister-in-law, April Burton, were in the country to celebrate Stefaniak's birthday, and Burton had been traveling with her for six days.

Burton left the country November 27, and Stefaniak's flight back to Florida was scheduled for the day after. The two were texting via WhatsApp throughout the day that Tuesday, Burton said, until Stefaniak suddenly stopped responding to her messages that evening.

And the following day, Stefaniak did not board her flight home.

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