BROOKLYN, Iowa (AP) — State and federal agents are investigating the disappearance of a 20-year-old University of Iowa student who has been missing for nearly a week from her hometown in eastern Iowa.

Volunteer searches for Mollie Tibbetts, of Brooklyn, were called off this week as the FBI and state investigators took over, Iowa Division of Criminal Investigation spokesman Mitch Mortvedt said Tuesday.

"We're still asking for the public's help," Mortvedt said. "We'd like to get any information we can. The more eyes and ears we have, the better."

Mortvedt said officials have little to go on, but they're "leaning more and more toward something happening to her against her will."

Television station KCRG reported Tibbetts was staying at her boyfriend's home at the time of her disappearance. She was there to watch his dogs because he had a construction job about 100 miles northeast in Dubuque. A neighbor reported seeing Tibbetts going for a jog last Wednesday evening.

The boyfriend, Dalton Jack, told the station he received a Snapchat photo from Tibbetts late Wednesday night, after she would have returned to the home from her jog.

She was reported missing Thursday when she didn't show up for work.

Mortvedt said FBI and Iowa investigators are concentrating on areas around Brooklyn that Tibbetts has known to have gone to in the past.

The FBI is also using an array of computer forensics — such as studying online history and cellphone app usage — in an effort to pinpoint where she might be, he said.

"This could shake out a bunch of different ways," Mortvedt said. "We are hoping and praying for the best outcome."

Dozens of volunteers in the town of about 1,500 had been searching fields around her house and the house where she was staying. They also blanketed the area with missing posters, T-shirts and billboard pleas for help in finding Tibbetts.

Tibbetts' aunt, Kim Calderwood of Brooklyn, told the Des Moines Register that Tibbetts' family is frustrated by the lack of progress in the search.

"We're racking our brains, thinking what can we think of to tell the investigators," she said. "It's the worst thing . to want to fix something you can't fix."