( CNN ) -- Two people have been detained in the death of a 43-year-old Montana schoolteacher last seen six days ago while out on a morning jog , law enforcement agencies said Friday . Sidney Public Schools , for which Sherry Arnold had worked as a math teacher at Sidney High School , announced that the school district learned of her death around 9:30 a.m. Friday . No other details were immediately available . Law enforcement officers have taken `` one adult male into custody , and another adult male is being questioned '' in relation to Arnold 's case , the FBI said Friday in a statement . `` The investigation to determine what happened to Ms. Arnold continues , '' the federal agency said . Sidney Police Chief Frank DiFonzo told reporters later Friday that law enforcement officers in North Dakota -- including members of the Williams County Sheriff 's Office , Williston police and the North Dakota Criminal Investigation Bureau -- helped arrest the first man , who is 47 years old . That man is now being being held in a Williams County , North Dakota , jail . The second male , age 22 , has been `` detained for questioning '' in Rapid City , South Dakota , added DiFonzo . The police chief declined to offer further details or answer questions `` because this investigation is rapidly moving forward . '' Arnold went running around 6:30 a.m. last Saturday in her small town in eastern Montana , but never returned home . Other than one of her running shoes found along her route , authorities had not indicated -- until Friday -- that there had been any sign of her . The woman 's disappearance rocked Sidney , located about 100 miles south of the Canadian border . It has a population of just under 5,200 people , according to the U.S. Census Bureau . A massive search effort involved hundreds of volunteers , as well as law enforcement authorities and National Guard members . Authorities on Wednesday `` determined the prudent course of action is to scale back the ground search . '' `` We 're such a small community , and crime is absolutely unheard of , '' said Christine Mullen , 26 , a CNN iReport contributor who joined the search effort , even though she did n't know Arnold personally . `` We do n't lock our car doors . ( We 're ) completely shocked . '' The FBI said Friday that `` dozens of tips were called into ( a ) tip line '' -- one of which led to the arrest and questioning . Sidney Public Schools said that all sporting events for Friday had been canceled and `` additional counselors ( were ) on hand '' to help students cope . In interviews with HLN 's Jane Velez-Mitchell earlier this week , the victim 's husband , Gary Arnold , said he was hopeful even as he admitted that the disappearance has been `` very difficult '' on the couple 's children . He said that he could n't fathom why anyone `` would harm her in any way . '' `` She is a good person . She 's kind , she 's sincere , '' Arnold said of his wife . `` She 's a great teacher , a referee , she 's a great wife and mother . ''
NEW : One man , 47 , is being held in Arnold 's home in North Dakota , a police chief says . NEW : Another man , 22 , is being ` ` detained for questioning '' in South Dakota , he says . Sherry Arnold was a teacher with the Sidney Public Schools in eastern Minnesota . She had last been seen six days ago out on a coffee run .