Kristin Smart, a freshman at California Polytechnic State University, San Luis Obispo, disappeared on May 25, 1996. Paul Flores was a longtime person of interest
Kristin Smart
Kristin Smart

A former classmate has been arrested on suspicion of murder in connection to the disappearance of Kristin Smart, a California college student who vanished in 1996 and whose body still has not been found, authorities announced at a Tuesday press conference.

Paul Flores, 44, a longtime person of interest in the case and a classmate of Smart's at California Polytechnic State University, San Luis Obispo, is accused of murder and is being held on no bail, San Luis Obispo County Sheriff Ian Parkinson said at the press conference.

His father, Ruben Flores, 80, was arrested on suspicion of accessory to murder and is being held on $250,000 bail, Parkinson said, who added that authorities are still searching for Smart's body.

"Until we return Kristin to them [her family] it is not over," Parkinson said. "We are committed to them. We are not going to stop until Kristin is recovered."

Paul Flores
Paul Flores
| Credit: San Luis Obispo County Sheriff's Office

Parkinson did not elaborate on what led to the charges against either suspect. He said that since 2011, the sheriff's office has served served more than 41 search warrants, did physical searches of many different locations, submitted more than 37 items for DNA testing, recovered 193 items of new physical evidence and conducted over 130 interviews.

"I am confident we have enough of a case to prove beyond a reasonable doubt," Parkinson said.

"Throughout our investigation Paul Flores has remained a person of significant interest," he added. "As the case progressed he became a suspect and the prime suspect in the case."

ruben Flores
Ruben Flores
| Credit: San Luis Obispo County Sheriff's Office

An attorney representing Flores, Sarah Sanger, told NBC News their firm will not comment on pending cases. Ruben Flores' attorney, Harold Mesick, declined comment to KSBY.

Smart vanished after attending an off-campus party on the Friday of Memorial Day weekend in 1996. Flores, now 43, was the last known person to see her alive after volunteering to walk her home in her inebriated state from the party, police have previously said.

In February and April of 2020, Flores was briefly detained but then released. Authorities said at the time they had searched Flores' home and that of his parents.

Kristin Smart
| Credit: Find Kristen Smart/Facebook

Want to keep up with the latest crime coverage? Sign up for PEOPLE's free True Crime newsletter for breaking crime news, ongoing trial coverage and details of intriguing unsolved cases.

Flores Was Longtime Person of Interest Who Became 'Prime Suspect'

After Smart vanished, campus police questioned Flores. When he was asked about a black eye he sported, he told police he got hurt in a pickup basketball game, but authorities grew suspicious when one of his friends later told authorities Flores already had the bruise when he showed up to play.

According to The Tribune of San Luis Obispo, he later admitted that was a lie and told authorities he got the bruise fixing his truck before ending the interview.

Later that year, after Flores had returned home for the summer, investigators from the sheriff's office searched his dorm room with four cadaver dogs, and the dogs keyed in on Flores's mattress, according to police.

Kristin Smart
| Credit: Axel Koester/Sygma via Getty

Despite remaining a person of interest in the case ever since, Flores had never been charged, until Tuesday.

He had remained mum about the case, invoking his Fifth Amendment right to remain silent when he was deposed in a 2005 wrongful death civil suit brought against him by Smart's parents, which they ultimately dropped.

PEOPLE has never been able to reach Flores for comment.

In 1998, his attorney told PEOPLE that authorities had no evidence against Flores.

"It's one thing to have suspicions," attorney Melvin de la Motte told PEOPLE, "but that doesn't make up for evidence."

PEOPLE was unable to reach de la Motte for comment after Flores' arrest.