(CNN) -- A California death row inmate has provided maps that led to the remains of two bodies and an abandoned rural well that has yielded 1,000 pieces and fragments of bone, authorities said.
Wesley Shermantine, one of two so-called "Speed Freak Killers," was sentenced in 2001 for four homicides, Deputy Les Garcia, public information officer for the San Joaquin Sheriff's Office, said Tuesday.
Authorities now are looking into whether there could be more buried victims.
They set up a hotline for relatives of missing persons who may have fallen victim to Shermantine and another man, between the mid-1980s and 2000, Garcia told CNN. They had received about 50 calls by late Tuesday.
Shermantine provided maps and letters to a reporter at the Stockton Record, who then forwarded them to investigators, Garcia said.
Searchers, aided by dogs, first went to sites in San Andreas in Calaveras County, he said. One of the pieces of property belonged to the Shermantine family.
Human remains were discovered.
The remains of Chevelle Wheeler, who disappeared in the 1980s, were tentatively identified, Garcia said. Authorities believe the other victim was Cyndi Vanderheiden.
The search for additional victims now is primarily focused on a 19th-century well near Linden, about 30 miles from where the two women's remains were found, Garcia said. Linden is 55 miles south of Sacramento.
"It is very tedious work," he said.
Since Thursday, searchers have dug down about 45 feet and have not reached water. They have no idea how many victims may be in the well.
"We are committed to collect all the remains that are humanly possible so that we can bring the loved ones to their families," Garcia said.
Besides hundreds of pieces of suspected human bone, investigators are unearthing purses, belts, coats, shoes and rings.
"The personal items and the clothing we are finding have been buried for over 20 years," he said.
Bounty Hunter Leonard Padilla told CNN on Monday that he promised Shermantine $33,000 for information leading to the remains of Wheeler and Vanderheiden.
About $18,000 was for the inmate's restitution and $15,000 was for headstones for Shermantine's parents' graves, he said.