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, law officers released the names of two men being held in the case and planned to hold a news conference at midday Monday.

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."

Williams County Sheriff's Deputy Jon Garrison said Walters and Spell face aggravated kidnapping charges in Montana.

Officials said Waters and Spell were brought to the Williston jail Friday. They declined to release where or how the men were taken into custody.

The jail is about 46 miles from Sidney, where officials say Arnold disappeared while on an early-morning run along a truck route on the edge of the oil boom town of more than 5,500 residents.

Sidney school officials posted a statement online Friday saying they learned of Arnold's death that day. The statement provided no details.

In the days after Arnold disappeared, hundreds of residents, police, firefighters and others combed the town and surrounding countryside without success.

The only clue that has been publicly released was that one of Arnold's shoes was found along her running route.

Arnold and her husband, Gary Arnold, have five children combined from prior marriages. Two live at home and attend the same school system where Sherry Arnold worked for the past 18 years.

Sherry Arnold's disappearance has taken a toll on the town, and "it's not over," Sidney Mayor Bret Smelser said Sunday.

"We're angry. We're frustrated," Smelser told The Associated Press. "But our concern is with Sherry's family and friends. And whatever support we can give to get them through this, that's what we'll do."