More human remains were recovered Thursday near the Northern California site where two victims of a convicted serial killer were recently found, authorities said.

Crews using cadaver dogs located the remains after expanding a search area near the Calaveras County community of San Andreas, said San Joaquin County Sheriff's spokesman Les Garcia.

Investigators have been searching the area after Wesley Shermantine led authorities to the site earlier this month. The search area is on property that Shermantine's family once owned.

Authorities are investigating if the newly found remains are from another victim of Shermantine and Loren Herzog, dubbed the "Speed Freak Killers" for their killing spree in the 1980s and 1990s. Garcia said the remains will be sent to the California Department of Justice Bureau of Forensic Services for analysis.

Shermantine has also led authorities to a well in San Joaquin County where investigators have found hundreds of human bone fragments.

Shermantine began disclosing where victims were buried after bounty hunter Leonard Padilla offered him money for the information.

Shermantine was convicted of four murders and sentenced to death. Jurors found Herzog guilty of three murders, but those convictions were later overturned after a judge determined his confession was illegally coerced. He instead struck a plea deal on one count of voluntary manslaughter and was paroled in 2010.

Herzog died in an apparent suicide last month, hours after receiving a call from Padilla to warn him that Shermantine planned to reveal the burial locations.

Using maps roughly drawn by Shermantine from his San Quentin State Prison cell, authorities first searched a remote Calaveras County property once owned by his family and found two sets of human remains. Tests have confirmed they belong to Cyndi Vanderheiden, 25, who disappeared in 1998, and Chevelle "Chevy" Wheeler, 16, who disappeared in 1985.

Shermantine was convicted of both murders in 2001, and Herzog's voluntary manslaughter plea was for Vanderheiden's death.