Rob Hess/ABC News
(BROOKLYN, Iowa) -- It's been 10 days since 20-year-old Mollie Tibbetts mysteriously vanished in a rural Iowa town, but investigators say they haven't given up hope that they will find her alive.
"At this point, we don't know her exact whereabouts but we continue to look. We are hopeful that she is still alive and so we will continue to think that way until told otherwise," Richard Rahn, special agent in charge of the Iowa Department of Public Safety's Division of Criminal Investigation, told ABC News on Friday night.
Data from Tibbetts' FitBit, a GPS-enabled activity tracker, has been "helpful" and could be "key" in locating her, according to Rahn.
"It certainly helps in that we are able to help establish a timeline and that's certainly critical for any investigation like this," he added.
Rahn declined to say whether investigators have found her FitBit or if they know its location.
Rahn told ABC News it's "not uncommon" to go back to a site and conduct additional searches as tips come in. He declined to reveal what clues if any investigators may have found at the pig farm. But he said one thing is for certain -- Tibbetts isn't there.
"I can tell you she's not there. Aside from that, I'm not sure what I'm able to release, but she's certainly not there," Rahn said.
Authorities 'hopeful' missing University of Iowa student is 'still alive' as search enters 10th day