The shocking story of a woman allegedly held captive 18 years in a rapist's back yard got even grimmer Friday evening, with reports that the rapist's Antioch, Calif., property is being searched for evidence in the murder of several prostitutes.

Contra Costa Sheriff's Department Capt. Daniel Terry said police officers from the nearby city of Pittsburg executed a search warrant Friday at the home of Phillip Garrido for clues in the unsolved slayings.

Several of the murdered women's bodies were dumped near an industrial park where Garrido worked during the 1990s.

Garrido and his wife, Nancy, were charged Friday with kidnapping 11-year-old Jaycee Lee Dugard in 1991. Authorities said they held her and two children she had with Garrido as prisoners in a backyard encampment.

The couple pleaded not guilty Friday at their arraignment on 29 counts, including forcible abduction, rape and false imprisonment. They both entered their pleas in El Dorado Superior Court, A judge ordered them held without bail.

Phillip Garrido, 58, appeared stoic and unresponsive during the brief hearing. His wife, 54, cried and put her head in her hands several times.

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The latest news comes on the heels of revelations that California police may have "missed an opportunity" three years ago to catch Garrido and rescue Jaycee Lee Dugard, the young woman he and his wife allegedly kidnapped when she was only 11.

Contra Costa County Sheriff Warren E. Rupf apologized Friday for what he characterized as an "organizational failure" in November 2006, when a neighbor called 911 to report that Garrido was psychotic, that there were people living in tents in his backyard and that children could be heard there.

Rupf said that on Nov. 30, 2006, deputy who responded to the 911 call spoke with Phillip Garrido in the front yard of his home and concluded that there was no criminal activity going on there. He said the officer at the scene apparently was not aware that Garrido was a sex offender, and the department failed to dig deeper and ask the right follow-up questions.

"This is not an acceptable (response). We should have been more inquisitive, more curious and turned over a rock or two. Our work should have resulted in a better outcome," Rupf said. "I cannot change the earlier course of events," he said. "We are beating ourselves up over this, and will continue to do so. ... There are no excuses."

Authorities said this week they finally were able to uncover the truth, that Garrido and his wife, Nancy, had kidnapped Dugard in 1991 and kept her in the backyard of their Antioch, Calif., home as Phillip Garrido raped her and fathered two daughters by her.

Dugard, now 29, was freed this week and reunited with her family as a clearer picture emerged of her life in the 18 years since she was kidnapped from a bus stop by her home in South Lake Tahoe.

PHOTOS: Missing Girl Found 18 Years Later

The Garridos are accused of keeping Dugard in an intricate backyard compound of tents, sheds and fences. Police suspect the Garridos of taking her straight there in 1991 after pulling her into their car at the bus stop about 200 miles away.

Garrido's father told The Associated Press on Friday that he believed his son is "absolutely out of his mind" after falling into a bad crowd when he was younger and taking LSD.

Meanwhile, Dugard's stepfather said she was reunited with her mother, and the family was "doing great."

Carl Probyn told CBS' "Early Show" Friday morning that he spoke to his wife Terry, from whom he is separated, late Thursday after she was reunited with her daughter.

"I think they're pretty happy," said Probyn, 60, counting the six people who were at the reunion: Dugard, her two daughters born during her alleged captivity, her mother, her sister and another relative.

The case broke after Phillip Garrido was spotted Tuesday with two children as he tried to enter the University of California, Berkeley, campus to hand out religious literature. Officers said he was acting suspiciously toward the children. They questioned him and did a background check, determined that he was a parolee and informed his parole officer.

Garrido was ordered to appear for a parole meeting and arrived Wednesday with Dugard, who identified herself as "Allissa," his wife, and two children. During questioning, corrections officials said he admitted to kidnapping Dugard.

People who knew Garrido said he became increasingly fanatic about his religious beliefs in recent years, sometimes breaking out into song and claiming that God spoke to him through a box.

"In the last couple years he started getting into this strange religious stuff. We kind of felt sorry for him," said Tim Allen, president of East County Glass and Window Inc. in Pittsburg, Calif., who bought business cards and letterhead from Garrido's printing business for the last decade.

Three times in recent years, Garrido arrived at Allen's showroom with two "cute little blond girls" in tow, he said.

Garrido, in a phone interview with KCRA-TV from the El Dorado County jail Thursday, said he had not admitted to a kidnapping and that he had turned his life around since the birth of his first daughter 15 years ago.

"I tell you here's the story of what took place at this house, and you're going to be absolutely impressed. It's a disgusting thing that took place from the end to the beginning. But I turned my life completely around," he said.

Phillip Garrido was convicted decades ago of kidnapping a 25-year-old woman whom he snatched from a South Lake Tahoe parking lot, handcuffed, tied down and held in a mini-warehouse in Reno, according to a November 1976 story in the Reno Gazette-Journal.

He also has a conviction for rape by force or fear stemming from the same incident, and was paroled from a Nevada state prison in 1988, according to the California Department of Corrections and Rehabilitation.

In 1991, police believe he was trolling for victims in South Lake Tahoe in a Ford Granada when he snatched Dugard from a bus stop outside her home. The case attracted national attention and was featured on TV's "America's Most Wanted," which broadcast a composite drawing of a suspect seen in the car.

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The Associated Press contributed to this report.