A classmate of California college student Kristin Smart, who vanished more than 20 years ago, was briefly detained in her disappearance and multiple search warrants were issued, according to reports.

Paul Flores, who was the last known person to see Smart alive, was held as one of the search warrants was served Wednesday at his San Pedro home, the San Luis Obispo Tribune reported.

He was released and allowed to re-enter the residence following the search of the home and two “vintage” vehicles, the outlet reported.

Warrants were also served Wednesday at two locations in San Luis Obispo County and another in Washington state, officials said.

Deputies and the FBI were seen Wednesday outside the home of Flores’ mother in Arroyo Grande, the Tribune reported. They were spotted carrying out various items, including what appeared to be a computer, into a van.

Over the years, Flores has refused to cooperate with authorities since an initial interview at the time of Smart’s disappearance.

Smart was a 19-year-old freshman when she went missing in 1996 from the campus of California Polytechnic State University at San Luis Obispo.

She was last seen near her dorm after walking home from an off-campus fraternity party and had been spotted with Flores, but he was never arrested or charged in the case.

Smart’s mom, Denise, drew media attention again to the case last month when she revealed a retired FBI agent recently contacted her and told her to prepare for a bombshell in the case, the Stockton Record reported.

She said the agency warned her, “Be ready. This is really going to be something you don’t expect.”

Kristin Smart was declared dead in 2002 though her body was never found.

With Post wires