(CNN) Colorado investigators trying to find Kelsey Berreth, a 29-year-old mother who went missing on Thanksgiving Day, have started searching her fiancé's home and property, authorities said Friday.

About 75 officers are combing the 30-plus acres outside Woodland Park, Colorado where Patrick Frazee lives, a law enforcement source told CNN. Frazee was at the home, which he does not share with Berreth, when officers arrived, but later left, the source said.

Kelsey Berreth hasn't been seen since November 22.

Woodland Park Police Chief Miles De Young provided few details at a news conference, declining to say what investigators are looking for or what prompted them to search that location. The search warrant is sealed.

But the chief said the disappearance of Berreth, a flight instructor, is considered "suspicious" and that authorities think "she is not intentionally avoiding attempts to find her."

De Young urged Frazee to consent to a face-to-face interview with police instead of communicating through his lawyer.

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