The search for evidence in the case of missing Colorado mom Kelsey Berreth has now extended to a landfill in the city of Fountain, ABC News reported Wednesday. The mother of one went missing on Thanksgiving Day and is now presumed dead.

A spokeswoman for Midway Landfill told ABC News that investigators were looking for more clues into Berreth’s disappearance amid search for the woman's body. The 29-year old flight instructor's fiancé Patrick Frazee has been arrested and charged with her murder.

“The Colorado Bureau of Investigation contacted Waste Management of Colorado regarding a potential search at Midway Landfill and we are cooperating fully,” Waste Management spokeswoman Anne Spitza said. 

The Midway landfill is a roughly 40-mile drive from Woodland Park, where Berreth was last seen shopping. Three days after Thanksgiving, Berreth’s cell phone pinged near Gooding, Idaho, just 40 miles from Twin Falls. Police believe the woman was murdered at her Woodland Park home. They said Frazee was the last person to see Berreth before she disappeared. 

Frazee was charged with five counts, including two counts of first-degree murder and three counts of solicitation to commit first-degree murder, on Dec. 31. Police also questioned Krystal Lee, a nurse believed to be Frazee's mistress, after suspecting she may have helped her alleged lover dispose of a cell phone that belonged to Berreth.

The Idaho couple who helped police with information that led to Frazee's arrest claimed in a new interview recently that the fiancé's mistress followed his orders out of fear. Lee had spoken to her best friend, who was an employee at the Rockstahls, saying that her partner asked her to "kill the mother of his child."

Joe and Patty Rockstahl, owners of Rockstahl Law Offices, came forward with information about Berreth after her mother Cheryl-Lee Berreth held a news conference on Dec. 10 pleading for the safe return of her daughter.

Police are currently trying to gather evidence that can help them understand the circumstances surrounding Berreth's disappearance. The cause of her death can only be determined after her body or remains is found.

Amid the investigation, a custody battle between Berreth’s and Frazee parents also broke out. The court ruled earlier this year that one-year-old Kaylee would remain in the custody of Berreth’s parents and child protective services. Frazee’s mother has since filed a motion to change the decision.

Berreth's family has also filed a wrongful death lawsuit against Frazee. In the complaint, they wrote Frazee "enacted physical, mental, and emotional acts of violence upon Kelsey Berreth prior to her death." It also states that "when Frazee acted as either the perpetrator or accessory to the murder of Kelsey Berreth, Frazee breached the duty of care with which a reasonable person should conduct himself toward another human being."