(CNN) 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, was last seen on July 18 near Brooklyn, a small community an hour east of Des Moines, according to the Poweshiek County Sheriff's Office.

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. She was last spotted jogging that evening, wearing gym shorts, a black sports bra and running shoes, the sheriff's office said.

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 Division of Criminal Investigation.

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