Twenty years since the most recent sighting of Kristin Smart, the California Polytechnic State University freshman who disappeared after a party, an excavation is underway to find her remains.

Police and the FBI announced they would start digging Tuesday on the San Luis Obispo campus where the 19-year-old Smart was last seen in 1996. The search officially began Wednesday morning.

The San Luis Obispo County sheriff’s office said that the digging comes as a result of a lead they “developed over the past two years that strongly suggested” Smart’s remains would be buried in the hillside where they are looking, according to ABC News. There are several other, undisclosed locations where police are searching as well. The operations are expected to take a few days.

Smart disappeared on the morning of May 25, 1996 after attending a party. She was walked home by three fellow party-goers after being found sprawled on the lawn next to the house holding the party.  Two of the people helping her get home later left the group, leaving Paul Flores to walk her home to her dorm. Flores was the last known person to see Smart alive although he said he let her finish walking on her own after he made it to his own dorm.

Campus police were slow in filing a missing persons report because they believed that Smart had simply gone on an impromptu vacation.

Flores has been considered a suspect for a long time, police say, but he has never been formally charged with the crime. Detectives and prosecutors cite a lack of evidence to prosecute him.

Early in the investigation, Flores was called in for questioning and, when pressed, he pulled himself into the fetal position.

“If you are so smart,” he said then, according to records, “then tell me where the body is.”

He later invoked his 5th Amendment right against self-incrimination when brought before a grand jury and during a civil deposition.