A US tourist vanished while celebrating her birthday in Costa Rica — and her family fears she may have been kidnapped.

The last time Florida resident Carla Stefaniak’s friends and family heard from her was the evening of Nov. 27, when she texted them to say the power in her San Jose Airbnb rental was going in and out, according to news reports.

Her last text message read: “It’s pretty sketchy here.”

The 36-year-old had been spending time in Costa Rica with her sister-in-law, April Burton, who went home last Tuesday, the Miami Herald reported.

Stefaniak was supposed to return to Miami the next day, Wednesday — and although she checked in, she never boarded her flight home.

An Uber driver who took Stefaniak sightseeing Tuesday and who was supposed to pick her up to go to the airport told the family he heard she left the rental home around 5 a.m. with her luggage and got into a mysterious car, according to the Herald.

The Airbnb owner and local security guards told the family the same story.

But Stefaniak’s family said that story doesn’t make sense, and they think something more nefarious is at play.

They say Stefaniak hasn’t used social media or Uber since she disappeared, which is unusual. And the fact that she checked in for her flight clearly shows she meant to come home, they said.

“We just know she has been abducted,” Burton told WFLA News. “There is no reason for her not to have any contact with anyone. It has been five days.”

Stefaniak’s brother, Carlos Caicedo, has traveled to Costa Rica to search for his sister.

“He said he’s not coming back until he finds her,” Burton told CBS News.

“She was just such a happy-go-lucky person. I’m just afraid she was just too trusting with someone there.”

Authorities in Costa Rica have also opened an investigation, and the family hopes the US government will get involved.