The property where Jaycee Dugard was held captive for 18 years became the site of an archaeological-style dig Friday as authorities revealed the discovery of another bone and a soil "anomaly" that could indicate something lies buried in an area where cadaver dogs earlier picked up a scent.

PHOTOS: Missing Girl Found 18 Years Later

Police from the cities of Dublin and Hayward have been searching the land to see if Phillip and Nancy Garrido, the couple charged with kidnapping Dugard in 1991, can be tied to two other Northern California child abductions from the late 1980s.

They cautioned that it was too soon to know whether the bone — one of several fragments recovered from the Garrido property and a neighboring parcel — or the presence of disturbed soil that indicates previous spadework were related to any crimes.

"It could be a lot of different things. It could be significant, and it could not be significant, but it's helping us target where we might do some digging," said Hayward Police Lt. Chris Orrey.

Orrey said Dugard, who was snatched outside her South Lake Tahoe home in 1991, has not supplied any information to indicate the Garridos were involved in the 1988 kidnapping of 9-year-old Michaela Garecht outside a Hayward market and the 1989 disappearance of 13-year-old Ilene Misheloff in Dublin.

"She's nosay they hid Dugard in their Antioch backyard. The Garridos have pleaded not guilty.

Investigators already have dismantled the hidden encampment of sheds and tents where authorities say Dugard was held and lived with the two daughters she had by Garrido. They also removed 19 truckloads of debris from the yard and looked inside the Garrido's house.

Orrey said they have taken "boxes and boxes" of papers in Phillip Garrido's handwriting.

"We will have to take it offsite and go through every single page to see if there's something significant," she said.

New photographs taken by Contra Costa County building inspectors at the request of the sheriff's department show the inside of the home cluttered with clothing, overturned mattresses and other debris.

Tables, couches, beds and other pieces of furniture also are buried under paperwork, toys, pillows and clothes. Piles of dishes spilled out of the sink; pots and bowls emptied onto the kitchen floor from overcrowded cupboards, the pictures showed.

Cords snaked through the house hooking up a computer, television and other electronics, and a fish tank was clouded with dirty water.

Despite the scientific scrutiny the yard is undergoing, Silva said the technology is not foolproof and that a significant piece of evidence could remain hidden deep underground.

"We will never walk away and say we have seen everything and there is nothing left in there. We can't make that determination," he said.