Police resumed their search Monday for possible links to unsolved crimes at the home of the Northern California sex offender charged with kidnapping a little girl and hiding her in his backyard for 18 years.

Three agencies in the San Francisco Bay area were looking through Phillip Garrido's property in Antioch for the fourth day, seeking evidence that might help solve cold cases.

Garrido and his wife, Nancy, were charged last week in the abduction, rape and imprisonment of Jaycee Lee Dugard, who was 11 when she was taken outside her home in South Lake Tahoe. They have pleaded not guilty to 29 counts.

Antioch and Contra Costa County authorities have not provided many details about what they are seeking at the property.

Police in the nearby city of Pittsburg, however, have said they are investigating whether Garrido, 58, was involved in the murders of prostitutes in the 1990s.

Over the weekend, authorities also roped off a next door neighbor's backyard where Garrido once lived in a shed. Neighbors say he once worked as the property caretaker and helped out an elderly man who lived there several years ago.