Investigators in Iowa have zeroed in on missing jogger Mollie Tibbetts' digital footprint, including her Fitbit -- which can capture GPS data -- as they work to solve her mysterious disappearance. 
 
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 Tibbetts, a 20-year-old rising sophomore at the University of Iowa, went jogging the evening of July 18 in her rural town of Brooklyn, Iowa, and never returned. She was reported missing the next day. 
 
 "She probably has on her Fitbit because she never takes it off," her boyfriend, Dalton Jack, said. "She uses it for the sleep tracker and for all her runs." 
 
 Facebook 
 
 Jack last saw his girlfriend July 16, he said. The next day, he went to Dubuque for his job at a construction company, while Tibbetts stayed at his house alone and watched his dogs, Jack said. 
 
 Going for an evening run, he added, was part of her regular routine. 
 
 Poweshiek County Sheriffs Office 
 
 "For a 20-year-old to go missing and completely kind of fall off the grid as far as social media, cell phone, banking activity, that kind of thing -- it’s obviously a very suspicious and very serious matter," Mitch Mortvedt, assistant director of field operations for the Iowa Division of Criminal Investigations, said. 
 
 KCRG 
 
 "She’s very well-connected through social media, cellphone, exercise equipment," Mortvedt said, "so we are trying to use that, obviously, to our advantage to gain any information that we can." 
 
 Poweshiek County Sheriff Thomas Kriegel added: "We do believe that there's going to be some useful information [from the Fitbit data] but [we are] not willing to share that.” 
 
 Fitbit Inc., which makes the activity trackers, declined to comment. 
 
 Rob Hess/ABC News 
 
 Police are also looking at surveillance video from businesses in town that are along the route Tibbetts she usually jogs, the sheriff said. 
 
 "She was kind of a creature of habit," Mortvedt, of the state Division of Criminal Investigations, said. "And about the same time every evening she’d go for a run during daylight hours; well before dusk or dark, and she was seen Wednesday evening on one of her normal routes." 
 
 Poweshiek County Sheriffs Office 
 
 In this close-knit farming community of about 1,500 people, everyone knows everyone, Sheriff Kriegel said. But the rural area makes the search difficult. 
 
 "We're surrounded by farm ground: corn and soybeans. Right now the corn is probably eight, nine feet tall. The only way you can search it is basically walk down every other row," he said. "It's difficult. Even the planes flying over have a difficulty looking down in the corn rows." 
 
 KCRG 
 
 KCRG 
 
 Meanwhile, Tibbetts' family is searching every field and every creek in town as they anxiously hope for answers. 
 
 One of Tibbetts' brothers, Scott Tibbetts, said he believes his sister is "fighting her best to get back home." 
 
 "She's a better fighter than anyone I know," Scott Tibbetts said. "So whatever situation she's in, it's not like she's going to sit there and give up." 
 
 Mollie Tibbetts' boyfriend and brothers are not suspects, Kriegel said. 
 
 Anyone with information can call the Poweshiek County Sheriff's Office at 641-623-5679. 
 
 ABC News' Alex Perez, Andy Fies, Rob Hess and Amanda McMaster contributed to this report. ||||| BROOKLYN, Iowa — In this Iowa town, Mollie Tibbetts' face is plastered everywhere, but the 20-year-old college student is nowhere to be seen. 
 
 "You never think you are going to see your sister on a poster with a missing sign right across it," said Jake Tibbetts, Mollie's brother. 
 
 Jake was the last to see her more than a week ago when he dropped her off at the house her boyfriend Jack Dalton lives in. 
 
 "I am just kind of putting trust and faith in the law enforcement," Dalton said. 
 
 Iowa Department of Criminal Investigation via AP 
 
 Dalton was out of town at the time of the disappearance and is not a suspect. Tibbetts went out on her usual evening run but never showed up at work the next day. Search teams have fanned out in the area and on her usual running routes. Now 15 FBI agents have also joined the investigation and officials are looking into Tibbetts' Fitbit and social media footprint for clues to build a timeline. 
 
 "That takes it to a whole new level, because we're hoping to be able to precisely examine and know where she was, when she was there," said Mitch Mortvedt, special agent in charge with the Iowa Division of Criminal Investigation. 
 
 Tibbetts' Fitbit could potentially give investigators a trove of data on the day she disappeared using GPS technology and other data like her heart rate. Investigators have also issued warrants to social media companies for data that could help determine exactly where she went. 
 
 "You can actually overlay the location data with the real world to find out what exactly happened," Thomas Yohannan, an expert on data recovery. "You are essentially trying to find a witness to the events that happened leading up to her missing person." 
 
 Late Thursday, investigators said they had completed reconstructing their timeline of Mollie's run, relying on Fitbit data, cell phone pings and eyewitnesses.
– With little else to go on, authorities are using Fitbit data in the effort to find a University of Iowa student who's now been missing for nine days. Mollie Tibbetts, 20, hasn't been seen since she went for a run in Brooklyn, Iowa, on July 18, but her boyfriend tells ABC News she was likely wearing her Fitbit because "she never takes it off." As the fitness tracker uses GPS, investigators hope to learn "where she was" and "when she was there," per CBS News. On Thursday, they announced a timeline of Tibbetts' run had been crafted using Fitbit and cellphone data, along with witness accounts. "For a 20-year-old to go missing and completely kind of fall off the grid as far as social media, cell phone, banking activity, that kind of thing—it’s obviously a very suspicious and very serious matter," Mitch Mortvedt, of the Iowa Division of Criminal Investigations, tells ABC.