After four days with no answers, authorities said they were considering scaling back their search for a Montana math teacher who left her home for a pre-dawn run and never returned.
The only publicized clue into Sherry Arnold's disappearance Saturday was a single running shoe, found by a ditch along her running route in her hometown of Sidney.
FBI agent Deborah Bertrand said late Tuesday that tips were starting to come into an automated hotline set up for the case, but would not offer any details.
The FBI and local law enforcement are investigating the possibility that Arnold, 43, was abducted from the town along the North Dakota border, which has been changing rapidly in recent years due to an oil boom.
Hundreds of residents, police, firefighters and others have been combing the town and surrounding countryside, but Bertrand said the operation may shift gears Wednesday, with authorities going door-to-door seeking information.
"At some point we feel like we've exhausted the possibilities in that area where she was last seen and apparently disappeared from," Bertrand said of a reason for the possible change. But she added that investigators were encouraged by tips coming into the hotline.
"We're glad to have all the attention we're getting. We want to get her name and face out there," Bertrand said.
Arnold, a popular math teacher who grew up on a ranch outside Sidney, is married to another school system employee, Gary Arnold. The couple has five children from prior marriages, including two living at home and attending the same school where their mother worked for the past 18 years.
The school district has played an active role in the search by lending buses to transport members of search teams and setting up a fund to defer expenses.
Mayor Bret Smelser said the effort had covered all of Sidney and surrounding areas of Richland County. He said federal agents had met with family members, including Arnold's parents, Ron and Sharon Whited, and pledged to press hard for answers.
"The promise they made Ron and Sharon was that they wouldn't give up until they had found something or found Sherry," Smelser said.
The telephone hotline for tips is 406-433-4027.