Police investigating two missing girl cases say cadaver dogs picked up a scent that could indicate buried remains in the backyard of the couple charged with kidnapping Jaycee Dugard.
Sgt J D Nelson of Alameda County Sheriff's Department said two dogs "indicated" a suspicious scent on a site in the backyard of Phillip and Nancy Garrido.
But he cautioned that the area is known to have buried remains from Native Americans and animals.
The Garridos are charged with the 1991 kidnapping of Miss Dugard, who was snatched outside her South Lake Tahoe home when she was an 11.
Prosecutors say they held her captive for 18 years. The couple have pleaded not guilty.
Since their August 26 arrest, their California home has become a focal point for investigators reviewing outstanding kidnap cases in the San Francisco Bay area.
Authorities are seeking evidence that may link the Garridos to the 1988 abduction of Michaela Garecht and the 1989 disappearance of Ilene Misheloff.
Sgt Nelson would not say where in the yard the dogs picked up a scent and warned of false positives.
Investigators plan to use high-tech radar equipment to scan the site and will start digging if the radar gives more specific information about what is underground, Sgt Nelson said.
Cadaver dogs are trained to sniff for the scent of a decomposing body.
"They picked up a scent that may or may not be a sign of some remains," Sgt Nelson said.
"The first dog was very tentative on its indication. The second dog was more direct and indicating directly."
On Wednesday, police recovered a bone fragment on the Garrido property and several more in a next door neighbour's yard that was also being searched by investigators because Phillip Garrido had access to it.
Tests are being done to determine if the bones are human or animal, officials said.
Investigators continued clearing trash and brush from the backyard that was littered with tents, sheds, an above ground pool and showers.
They have also collected personal items that they would not identify that belong to Miss Dugard.