Investigators hope data from a missing Iowa woman's Fitbit may give them clues to her whereabouts after her disappearance last week.
Mollie Tibbetts, 20, vanished on July 18 in Brooklyn, a small community an hour east of Des Moines.
On the day she disappeared, Tibbetts' brother dropped her off at her boyfriend's house so she could dog-sit, reported HLN, CNN's sister network. Investigators said a neighbor saw the University of Iowa student running later that night, according to HLN.
Days after her disappearance, the search for the woman has intensified. The FBI joined the investigation this week, devoting as many as 15 agents to the search that has involved an army of volunteers.
Investigators have executed search warrants for Tibbetts' Fitbit, which she was known to wear, and her Snapchat, Instagram and Facebook accounts, said Mitch Mortvedt, spokesman for the Iowa Department of Criminal Investigations.
"This is a new arena for us. That's part of the reason we called the FBI in. It's probably pretty new to them, too," Mortvedt said. "I don't know of another case here in Iowa where we have used specifically Fitbit info."
He said he hopes that information will give investigators details such as the route Tibbetts took before she disappeared.
More FBI agents on the way
In an interview Wednesday on HLN, Tibbetts' mother, Laura Calderwood, said the family was told they would get an FBI agent for the case.
"That turned into approximately 15 FBI agents," she said.
"In my morning brief this morning, I have been told there's more on the way," Calderwood said.
Earlier this week, Tibbetts' boyfriend, Dalton Jack, told CNN affiliate KCRG he was one of the first people to notice she was missing.
"I was the one who threw red flags," he told the affiliate.
Jack said he was in Dubuque for work and his brothers were in Ames while Tibbetts was dog-sitting at his house, the station reported.
He grew worried and knew something was wrong when she didn't show up to her job last Thursday.
"She hadn't called in," he told the station. "I looked at my phone and noticed I texted her good morning that morning and she hadn't looked at it. So, I got ahold of her friends and family."
Search crews began searching that day, focusing on the fields between Tibbetts' house and where she was staying when she disappeared, KCRG reported.
Tibbetts' brother Jake Tibbett told CNN affiliate KCCI he never thought he would see his sister on a missing poster.
He said he's played "every possible scenario a billion times."
"I can never land on one," he said. "That's probably the toughest part."
'Let's find her'
Officials said abduction is one of the possibilities they are exploring, KCRG reported.
Tibbetts' family started a Facebook group dedicated to finding her, according to a post by a family member, Sandi Tibbetts Murphy. The group had more than 27,000 followers by Wednesday night.
"Please keep sharing Mollie's information so we can bring our girl safely home," Murphy wrote.
Calderwood said friends she hasn't talked to in years tracked down her cell phone number to say, "wishing you the best."
She said her daughter was born in Oakland, California, but the family moved to Brooklyn when Tibbetts was in fourth grade, KCRG reported.
Calderwood told HLN she knew people were praying for her daughter's safe return.
"I see the pain in my boys' eyes every day," she said. "I've got to stay strong for them."
That resolve could be heard in her voice.
"Just remember Mollie," Calderwood said.
"Let's find her."
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