Investigators have seized two trucks as evidence that belonged to the family of a prime suspect in the cold case disappearance of California college student Kristin Smart who vanished 24 years ago.

Authorities revealed details of the new evidence on Wednesday in a long-awaited investigation update in the 1996 disappearance of the 19-year-old Cal Poly student.

The two trucks now in evidence were confiscated from the family of Paul Flores - the Cal Poly student who was the last known person to see Smart the night she vanished.

Flores has long been the primary suspect in Smart's disappearance but he has never had any charges filed against him.

Authorities investigating the 1996 disappearance of 19-year-old Kristin Smart revealed on Wednesday they had new evidence in the case

In addition to the two trucks, the San Luis Obispo County Sheriff's Office said they had submitted 37 pieces of evidence from the early days of the investigation for modern DNA testing.

Paul Flores is the Cal Poly student who was last known person to see Smart the night she vanished. He has long been the primary suspect in Smart's disappearance but he has never had any charges filed against him

Authorities also revealed they have recovered 140 new items of evidence, carried out 18 search warrants and conducted 91 interviews since 2011.

The sheriff's office disclosed that they have spent about $62,000 in investigative expenses related to the Smart case.

Authorities took the unusual step of releasing the case update following the large number of public inquiries related to Smart's disappearance.

The case was recently catapulted back into the public eye due to a local podcast about the Smart investigation.

Smart's mother also revealed earlier this month that she had been contacted by a former FBI agent who warned her to be ready for news related to her daughter's case.

Smart was last seen in the early hours of May 15, 1996 when she returned to her dorm after a party near the California Polytechnic State University campus.

The San Luis Obispo County Sheriff's Office said they had submitted 37 pieces of evidence from the early days of the investigation for modern DNA testing in relation to Smart's disappearance

Smart was last seen in the early hours of May 15, 1996 when she returned to her dorm (pictured above) after a party near the California Polytechnic State University campus

Authorities also revealed they have recovered 140 new items of evidence, carried out 18 search warrants and conducted 91 interviews since 2011

Flores was the last person to see her alive, according to investigators.

He told police at the time that he walked Smart back from the party but parted ways with her about a block from her dorm.

She was reported missing two days later by a friend but a search didn't begin until days later due to a miscommunication between authorities.

During the investigation, four different search dogs trained to pick up the smell of human remains led police to Flores' dorm room.

No evidence was found in Flores' room.

Smart was officially declared dead in 2002 but her body has never been found.

Various search efforts have been carried out over the years, including the excavation of three different hillside locations near the campus in 2016.

At the time, an investigator said a lead strongly suggested her remains might be buried near a large concrete letter 'P' that is the school's landmark.

The search ended with no trace of Smart's remains.

Smart was officially declared dead in 2002 but her body has never been found. Her parents and siblings are pictured above after she vanished