A man kidnapped 9-year-old Michaela Garecht in 1988 from a market near her home in Hayward.
Death Row inmate Wesley Shermantine has claimed his childhood friend, Loren Herzog, abducted Garecht. Herzog committed suicide in prison last month and Shermantine has promised, but so far failed to reveal where the bodies of three people he was convicted of killing are buried.
Shermantine and Herzog are suspected of murdering up to 25 people during a methamphetamine-fueled spree that lasted until their arrests in 1999.
Associated Press contributed to this report.