"We do consider it a crime scene," said Jimmy Lee, a spokesman for the Contra Costa County Sheriff's Department.
Lee would not elaborate on what kind of evidence investigators were seeking or the nature of the possible crimes involving the second property. The link to the kidnapping case is that Phillip Garrido, the man charged with holding Dugard in captivity for 18 years in his own backyard, had access to the neighboring land when the house that sits on it was vacant three years ago.
"It looks like Garrido lived on the property in a shed," Lee said.
Damon Robinson, who moved into the vacant house in 2006, and another neighbor say Phillip Garrido served as caretaker of the home before Robinson took occupancy. That same year Robinson's then-girlfriend called police after she saw tents and children in the backyard, but the responding deputy did not uncover the backyard compound.
A third neighbor, Janice Deitrich, 66, said that Phillip Garrido visited and helped to feed an elderly neighbor who lived in the house before Robinson.
Police in Pittsburg, a Bay Area city near where the Garridos lived, have said they are investigating whether Phillip Garrido may be linked to several unsolved murders of prostitutes in the 1990s. Antioch police are also looking into unsolved cases but declined further details.
"We will take a close look at if there are any links to open cases," Lee said, declining to provide additional details.
Authorities on Sunday removed two paper grocery bags filled with papers from Garrido's primary residence, which he shared with his wife and mother, and boarded up the structure's windows. Searches of both parcels were expected to continue on Monday, Lee said.
Investigators also continued clearing brush from the scruffy backyard compound of tents and sheds where Garrido and his wife, Nancy, allegedly took an 11-year-old Dugard in 1991 after abducting her. Dugard and the two daughters, now 11 and 15, she had by Garrido lived in the secret encampment, authorities allege.
The compound was concealed by thick foliage, trees and tall fences, and authorities say it was equipped with a makeshift shower and an outhouse. The structures were lit by lights powered by extension cords, and one shed was soundproofed and set up with access controlled from the outside.
Karen Walker, 58, who has lived two doors down for the last five months, said the Garridos had a fire recently in a van parked on their property. When neighbors went to investigate, Phillip Garrido "shooed people away," Walker said.
Like many others on their street, Walker could not recall ever seeing Jaycee Dugard, but remembered seeing two shy young blonde girls.
Walker said her 9-year-old grandson once asked the younger of the two girls if she wanted to play.
"They asked if they could ride bikes with her, just being friendly, but she said she couldn't," she recalled.
Other neighbors said they pointedly kept their distance from a man they nicknamed "Creepy Phil," partly because he ranted about hearing voices from God, and because some knew that he was a registered sex offender. But they assumed parole authorities were keeping a close watch on their eccentric neighbor, who was convicted three decades ago of abducting and raping a casino worker in a Nevada warehouse that a former detective described as a "sex palace" for playing out his fantasies.
But even though Garrido wore an ankle bracelet tracking device and received visits from his parole officer, they did not find out about Dugard or the secret compound. And a sheriff's deputy, following up a neighbor's complaint that there were girls and tents in the backyard, left after concluding there was nothing more than minor building code violations.
Neighbors said they did not see Dugard but they saw two shy young blonde girls who, it turned out, were Dugard's daughters.
The customers of Garrido's business card and brochure company knew Dugard as Allissa, the polite, efficient assistant and the business owner's daughter. They talked with her on the phone and exchanged emails.
At least one customer, Ben Daughdrill, also saw her in person twice in the last six months when he drove to the Garrido home to pick up office supplies and pay for them.
She came out alone to Daughdrill's vehicle and conceivably could have escaped or asked for help.
"There was a reason she did not say anything," said Daughdrill.
By then, she was mother of two girls, now ages 11 and 15, sired by Garrido.
The secrets of the Garrido home began to surface early last week when he and his two daughters went to the University of California at Berkeley. He wanted to leaflet and hold an event on the campus, but the events coordinator and a campus police officer thought he behaved strangely and were concerned about the robotic behavior of his daughters.
When the officer found that Garrido was a registered sex offender with a rape conviction in Nevada, she contacted his parole officer.
At a meeting with his parole officer, Garrido brought along his wife, Dugard and the two girls. Authorities say he confessed to snatching Dugard from a South Lake Tahoe bus stop in 1991 and was arrested along with his wife.
Dugard, now 29, was reunited with her mother, sister and another relative Thursday. Her stepfather says her two children remain with her and she is healthy although she feels guilty about developing a bond with Garrido.
"Jaycee has strong feelings with this guy. She really feels it's almost like a marriage," said Carl Probyn, who had witnessed the kidnapping and tried to give chase.
Phillip and Nancy Garrido pleaded not guilty Friday to a total of 29 counts, including forcible abduction, rape and false imprisonment.
Associated Press writer Terry Collins in Antioch contributed to this story, with reporting from Cathy Bussewitz.