San Luis Obispo County sheriff’s detectives searched four locations Wednesday morning as part of the decades-old Kristin Smart missing-person case, serving search warrants in the Central California county as well as Los Angeles County and Washington state.

Investigators served two warrants in San Luis Obispo County, the area where the 19-year-old Smart disappeared in 1996 when she was walking back to her dorm room from a party. She has never been found and detectives presumed she was dead years ago.

The 24-year-old case has received renewed interest following a popular podcast, “Your Own Backyard,” which focused on the last person to see Smart alive, fellow Cal Poly student Paul Flores. Law enforcement has focused its investigation over the years on Flores and his family.

FBI and sheriff’s agents searched the house of Flores’ mother Wednesday morning, blocking off the property with crime tape, according to the San Luis Obispo Tribune.

Detectives would not comment on what was searched around 7 a.m. at the four locations, saying the warrants were sealed. However, Flores’ family still lives in San Luis Obispo County and investigators have searched those properties in the past. Flores lives in Los Angeles County.

The Sheriff’s Office said it is searching for “specific items of evidence inside four separate locations in California and Washington.”

“The search warrants are limited in scope, and sealed by the court,” officials said in a statement. “As a result, we are precluded by law from disclosing any further details about them.”

A Smart family spokesman said they had no comment about the developments and didn’t know any details.

Last week, investigators acknowledged they seized two trucks formerly owned by the Flores family, one from out of state.

The Sheriff’s Office, which has taken criticism for how it handled the investigation in the months immediately after Smart went missing, provided new information last month about its efforts in the case since 2011, when current Sheriff Ian Parkinson took over the office.

Before Wednesday, the department had served 18 search warrants, completing physical evidence searches at nine locations, and re-examined every piece of physical evidence in the case while also submitting 37 items of evidence from the early days of the case to a lab for modern DNA testing, officials said.

The department also recovered 140 new items of evidence, conducted 91 person-to-person interviews and has written 364 supplemental reports.

A team of sheriff’s investigators and forensic specialists are working Smart’s case, which has incurred $62,000 in expenses that includes DNA testing, officials said. That cost does not account for more than 7,500 employee hours on the case in the last nine years.

The family recently told the Stockton Record that the FBI alerted them to a big break in the case. However, the FBI denied talking to the family and it became clear a former agency employee spoke to the family.

Matthias Gafni is a San Francisco Chronicle staff writer. Email: matthias.gafni@sfchronicle.com Twitter: @mgafni