Investigators say 29-year-old Kelsey Berreth, a Colorado mom who hasn't been seen since Thanksgiving, remains missing after detectives executed a search warrant at her fiancé's 35-acre property over the weekend. 

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A multi-jurisdictional task force executed the search warrant at Patrick Frazee's property in Florissant over the weekend, which is about 15 miles west of Woodland Park where Berreth was last spotted. 

"There were approximately 75 people involved in yesterday's search," a release from the Woodland Park Police Department read in part. "The search is complete and the property has been turned back over the homeowner."

A backhoe was also brought in to the search the property, "as we continue to be a thorough as possible," the release continued. 

Berreth was last seen in surveillance video shopping at a Safeway store with her daughter in Woodland Park on Nov. 22. Cheryl Berreth, Kelsey Berreth's mom, first reported her missing on Dec. 2 after she contacted Frazee and said she had a difficult time getting ahold of her, according to law enforcement.

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Woodland Park Police Chief Miles De Young said investigators believe Frazee is the last person to have seen her in person when the two exchanged their 1-year-old child. Last week, Frazee said through his attorney that he voluntarily released his phone to law enforcement for a search and provided buccal swabs and photographs.

Berreth's phone pinged in Gooding, Idaho on Nov. 25. She has family in Idaho and Washington, according to a missing persons bulletin for the case.

The same day her phone pinged in Idaho, De Young said she sent a text to her employer and said she wouldn't be in the next week.

On Saturday, the Woodland Park Police Department said information leading to the location or safe return of Berreth is eligible for a $25,000 reward.

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No suspects have been identified in the case.