Authorities investigating the reported death of a Montana school teacher asked land owners in parts of Montana and North Dakota to check vacant farmsteads for signs of disturbed soil or matted grass, saying her body might be buried at such a site.

As new details about 43-year-old Sherry Arnold’s mysterious disappearance emerged Sunday, law officers released the names of two men being held in the case.

Lester Vann Waters Jr., 47, and Michael Keith Spell, 22, both of Parachute, Colo., were in the Williams County Correctional Center in Williston, N.D., awaiting extradition to Montana, authorities said.

The FBI issued a statement late Sunday saying the body of the Sidney, Mont., woman might be buried in a “shelter belt,” or a line of trees that protects soil from the wind.

The agency asked that property owners in three North Dakota counties — Williams, McKenzie and Mountrail — and in extreme northeastern Montana check vacant farmsteads for signs of disturbed soil or matted grass. Landowners who discover something unusual should not disturb the area, but call authorities, the FBI said.

“Based on investigative evidence gathered over the last few days, it is believed that Ms. Arnold may be deceased,” FBI spokeswoman Debbie Bertram said in a statement. “Her body has not been recovered.”