An unidentified 32-year-old nurse from Idaho is being questioned in the Kelsey Berreth case. According to ABC News, police believe the woman, believed to be an accomplice of Patrick Frazee, Berreth’s fiancé, may have been involved in disposing of a cell phone belonging to the missing Colorado woman, who cops believe is dead.

The latest development in the case comes as prosecutors came up with two theories regarding the death of the 29-year-old. Court documents filed Monday revealed that Berreth’s fiancé attempted to procure someone to kill the mother of one three times between September and November. Reports said Frazee had been working on a murder plot just a few months after Berreth purchased a home in Woodland Park, Colorado, for her and her infant daughter Kaylee. According to the Daily Mail, Berreth spent $184,900 on a two-bedroom property about 15 miles away from the ranch where Frazee lived with his mother.

Frazee was charged on five counts of murder relating to her death, including two counts of first-degree murder and three counts of solicitation to commit first-degree murder, on Dec. 31. When Frazee was arrested Dec. 21, police said more arrests were possible.

Berreth was last seen on Thanksgiving Day with her daughter at a Safeway in Woodland Park. Three days after Thanksgiving Day, 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.

The nurse's identity is being withheld because she has not been charged, the Daily Mail reported, adding that no other details were revealed. Authorities have yet to discover a body or any of Berreth's remains. However, police said they had found possible evidence in connection to the case.

Frazee will be back in court Friday for a four-hour motions hearing in his upcoming murder trial. Court documents show that Frazee will be fighting the charge of first-degree murder. He may also appear at the Teller County Courthouse on Thursday for a motion filed by his mother late December requesting custody of her son's daughter Kaylee.

Last week, a judge granted physical custody of Berreth’s one-year-old daughter to her maternal grandparents. Since then, a custody battle has brewed up between the two families. A family member claimed that just before her disappearance Berreth had split with Frazee, with whom she had Kaylee. However, this was never confirmed by investigators.

Berreth's parents are "absolutely devastated" after learning that their daughter might have been killed. Her cousin Jodi Garretson told Inside Edition: "I can't even fully comprehend how horrible they have to be feeling. That's their only daughter.”