The father of a missing Iowa college student believes she may have gone willingly with someone she had trusted.
Mollie Tibbetts has been missing for nearly three weeks. She was last seen July 18 by a neighbor while out for a run in Brooklyn, Iowa. She had been dog-sitting for her boyfriend and his brother at the time.
"It's totally speculation on my part, but I think Mollie is with someone that she knows, that is in over their head," her father, Rob Tibbetts, told Fox News.
He added that he believed there may have been "some kind of misunderstanding" that has led to the disappearance.
Tibbetts' boyfriend, Dalton Jack, was out of town at the time for work and is not considered a suspect in the case.
Although she was last seen while on her run, her family previously told the media there was some evidence she may have returned to the house and may have been doing homework on a computer.
Her father believes a person she trusted may have shown up at the house and that Tibbetts may have initially left willingly, he told CBS News.
"The longer we go without finding Mollie's body, the more hopeful we are that she's alive somewhere and going through something that she can survive," Tibbetts said to Fox News.
He encouraged anyone who may have his daughter to let her go before anything escalates. A reward for information in the case has grown to more than $277,000, according to CBS News.
Investigators have been looking into all possibilities in the disappearance and have released few details about the evidence they've discovered.
They have not classified the disappearance as an abduction but have said the disappearance is not consistent with Tibbetts' past behavior.
Last week, investigators questioned a pig farmer repeatedly in connection with the case, but have not revealed whether he is considered a suspect.
A neighbor also reported seeing a suspicious black SUV circling the neighborhood the night Tibbetts disappeared.
[Photo: Photo: Poweshiek County Sheriff's Office]