Kristin Smart missing
Kristin Smart vanished in 1996 while walking home from party to her dorm at California Polytechnic State University.Facebook/Kristin Smart

Police and the FBI have begun digging up a section of a southern California university campus in the hope of finding the remains of a long-missing female student. California Polytechnic State University freshman Kristin Stewart, 19, vanished in 1996 while walking home to her dormitory after a party near the San Luis Obispo campus.

The digging operation is excavating spots in three locations on a hillside behind Stewart's dorm complex and near the Cal Poly "P" landmark sign. The new search was triggered by the development of a lead that emerged after an exhaustive two-year re-examination of the evidence that "strongly suggests" Smart's remains might be buried there, said county Sheriff Ian Parkinson.

Human remains detection dogs from the FBI also searched the area earlier this year and signalled "locations of interest" in that area, according to the sheriff's office.

"Until it's done, we want to continue to manage our expectations," Parkinson said. "We're hoping that we find something, and we're committed to not stopping until we're able to bring this to a closure.

"It is our hope and desire this leads to some of the answers. We'll not give up."

Parkinson said the operation will last a few days. The university's fall session doesn't begin for another two weeks. Right now machine excavators are dropping piles of dirt on a deck where investigators sift through the earth seeking any hint of human remains or other evidence.

"We have people going through it with rakes and shovels trying to find anything of evidentiary value," FBI Special Agent Tom Brenneis told the San Luis Obispo Tribune. "Once we find something, then we'll hone in on it and it will get down to brushes and trowels, more like an archaeological dig."

"We are encouraged and hopeful for the new developments in Kristin's case," said a statement from her family.

"We have been hoping, praying and waiting for the last [20] years for the return of our daughter. While it is our fervent prayer for Kristin to be recovered and returned to our family with this effort, our hopes are tempered with the history of the last two decades."

Despite the new search the sheriff said authorities are not any closer to making an arrest.

But Paul Flores, a t fellow freshman who told authorities he escorted Smart to her dorm, remains a person of interest in her disappearance, police said.

Cal Poly spokesman Matt Lazier told ABC News: "Our hearts continue to go out to the family of Kristin Smart. We cannot imagine the pain they have endured over the years and hope this investigation leads to answers."