The bones were found in an abandoned well in Calaveras County on Saturday. Authorities were led there by death row inmate Wesley Shermantine.
Two sets of remains had been found Thursday and Friday near property once owned by Shermantine's family about 60 miles south of Sacramento.
In the 1980s Shermantine and his friend, Loren Herzog, became known as the "Speed Freak Killers" after going on a methamphetamine-fueled murder spree that had as many as 15 victims. The pair never disclosed where they dumped their victims.
Shermantine was convicted of four murders and sentenced to death. Herzog was convicted of three murders and sentenced to 77 years to life in prison, though that was later reduced to 14 years.
According to the Los Angeles Times, Shermantine agreed to give up the information for $33,000. That's enough to pay off his restitution order, as well as buy a TV and other comforts for his cell on death row.
The search was called off after dark Saturday, but was set to resume on Sunday.
The Associated Press contributed to this story.