After investigators found additional bone fragments on Jaycee Dugard's accused kidnappers' property, cadaver dogs reacted at a spot on the property's soil.
"The first dog, by their description, was very tentative on his indication," said Sgt. J.D. Nelson of the Alameda County Sheriff's Department. "The second dog was more direct and indicating very directly."
Police cautioned that under some circumstances cadaver dogs will give a false positive. On Friday, authorities will begin using archeological dogs -- dogs that are able to detect older bones.
Additionally, it is not known whether the new bone fragments found on Garrido's property are human or animal bones.
Searchers likely will use ground penetrating radar and a magnetomer, technology that can read down 20 feet into the ground, before deciding to excavate on the spot where the dogs indicated.
"It's an open ground area," said Lt. Christine Orrey of the Hayward, Calif., Police Department. "We're going to run the X-ray equipment that I talked about over it ... to get a subterranean look at things, and we will eventually be digging in that location."
Investigators have been seen ripping down the sheds and tents on Garrido's property, and also crawling on their hands and knees, patting the ground and sifting through soil. Garrido and his wife, Nancy, allegedly kept Dugard prisoner in their backyard for 18 years, and officials have said he is the father of her two children.
While the search could go on for days, authorities said so far they've found nothing that breaks open the cases of 9-year-old Michaela Garecht and 13-year-old Ilene Misheloff, who were kidnapped in 1988 and 1989.
Police from Hayward and Dublin, Calif., where the girls disappeared, said this week they would be going through the Garridos' property, looking for evidence based on similarities between their abductions and that of Jaycee Dugard in 1991.
Michaela was snatched on a trip to a Hayward grocery store in broad daylight, and Ilene vanished on her way home from school.
An earlier search by police on the Dugard case, also of the Garridos' backyard and an adjacent property, turned up a bone fragment that was later determined to likely be human.
Investigators are planning to rip into the sheetrock at the Garridos' home, and are considering the possibility of razing the entire structure.
The lead official of the Hayward Police Department declined an interview today. Messages left with the Dublin Police Department were not immediately returned.
The two police departments are receiving assistance from teams of trained professionals, including the FBI.
Bob Lowery, executive director for the National Center for Missing and Exploited Children's missing children's division, said the composition of a backyard can still yield clues even 20 years later.
While Lowery is not involved in the physical search in Antioch, he has participated in similar evidence-gathering missions as commander of a violent crimes task force in St. Louis.