By Laura Zuckerman
SALMON, Idaho (Reuters) - The FBI and police in Montana were investigating the suspected abduction of a high school math teacher reported missing over the weekend and believed to have been taken out of state, authorities said on Tuesday.
Sherry Arnold, 44, was last seen setting off for a run on Saturday morning in her hometown of Sidney, a small agricultural community in northeastern Montana. Her husband, Gary Arnold, later reported her missing, police said.
FBI spokeswoman Deborah Bertram said wide-ranging searches organized by authorities and conducted by hundreds of volunteers have unearthed at least one vital clue -- a running shoe owned by the missing woman, who has been teaching for 21 years.
Law enforcement officials suspect she was the victim of a kidnapping, Bertram said, adding that the FBI gets involved in such cases when missing persons are believed to have been taken against their will across state lines.
Bertram said federal agents were developing several leads from calls to a tip line but declined to disclose details.
"This is an active case. We're not discussing the evidence because we don't want to jeopardize our investigation," she said.
(Editing by Mary Slosson and Steve Gorman)