WARWICK, N.D. -- A body found Tuesday in the Sheyenne River has been identified as Amanda Stach Engst, a 36-year-old missing woman who may have been connected to a couple police say went on a robbery and burglary spree.

Engst’s body was discovered after a morning-long search by the Jamestown Fire Department Dive Rescue Team using an underwater camera on a remotely operated vehicle (drone), Eddy County Sheriff Paul Lies said. He declined to comment on a possible cause of death other than to say it did not appear to be natural. The body was sent to the UND Forensic Pathology Department in Grand Forks for an autopsy.

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The search was conducted along a stretch of the Sheyenne River south of Warwick on the Spirit Lake Indian Reservation, which lies partly in Eddy County, he said.

“Based on information we had received, we contacted the dive team to search that area of the river,” he said.

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The FBI is leading the investigation, he said, and the North Dakota Bureau of Criminal Investigation, Devils Lake Police Department and several county sheriff’s departments in the region are also involved.

Late last week, the Herald reported a possible link between Engst's disappearance and a string of robberies in North Dakota and Minnesota.

Her vehicle was discovered in the possession of Billy Joe and Crystal Marie Herman, both 36, when the two were arrested separately late last year in connection with the October robberies and burglaries.

The Hermans were sentenced last month in connection with an Oct. 30 bar robbery in Buxton, N.D. They still face multiple charges in other robberies or burglaries at businesses in Perley, Minn., and Grandin, N.D.

Billy Joe Herman is serving a one-year sentence at the North Dakota State Penitentiary in Bismarck. Crystal Herman is incarcerated at the Northwest Regional Corrections Center in Crookston.

Norman County Sheriff Jeremy Thornton said authorities have no reason to believe that Engst might have been involved in the robberies.

Engst grew up in Breckenridge, Minn., but had lived recently in Fargo and Halstad, Minn., family members said, adding that the last place they had heard she had been was in Warwick.

Engst last had contact with her family in late October, though family members initially reported her missing in November.

On Saturday, Engst's mother, Denise Stevenson, told the Herald her daughter was acting differently the last time she saw her at a family funeral in September. She added Engst had mentioned befriending a man she referred to as “Billy,” whom Stevenson said she believes is Billy Joe Herman.

“Amanda (Engst) is a very loving, giving person, … but her whole demeanor changed,” Stevenson told the Herald. “Something was really off when she came here in September. She wasn’t right. She was angry, she just flew off the handle over anything, got mad at everybody. I don’t know what was going on.”