A convicted rapist accused of kidnapping an 11-year-old girl and holding her captive for nearly two decades may also be responsible for a string of prostitute murders, California police say.

On Friday, officers executed a search warrant at the home of Phillip Garrido, 58, looking for fresh evidence that could link him to several unsolved murders in California's Bay Area.

In the 1990s, police found the remains of several women in an industrial area not far from Garrido's former workplace.

Meanwhile, officers say they missed an opportunity in 2006 to bust Garrido, who allegedly held Jaycee Lee Dugard and the two children he fathered with her in a backyard compound for several years.

In November 2006, police went to Garrido's home after getting a complaint about a collection of sheds and small buildings in his backyard.

But the investigating officer failed to uncover the three alleged captives.

"I cannot change the course of events. But we are beating ourselves up over this," said Contra Costa County Sheriff Warren E. Rupf on Friday.

He added that an officer simply dismissed the complaint about the camp ground-like setup in Garrido's backyard.

"He did not enter, nor request to enter the backyard. This is not an acceptable outcome. Organizationally, we should have been more inquisitive, more curious and turned over a rock or two."

Garrido, 58, is accused of kidnapping Dugard in 1991 when she was 11-years-old.

Authorities finally learned that Dugard was still alive on Wednesday, after she showed up at a police station with Garrido.

Garrido had been ordered to report to his parole officer after he had been seen acting suspiciously toward two young girls the day before at the University of California campus in Berkeley. Police say he was trying to enter the campus to hand out religious literature.

When explaining the situation to his parole officer, he initially claimed that Dugard was his wife and the young girls were his children.

Corrections officials say that after further questioning Garrido admitted to kidnapping Dugard.

Garrido is being held for investigation of various kidnapping and sex charges. And he is suspected of raping Dugard and fathering her two young children.

Investigators say his 54-year-old wife, Nancy Garrido, was present when Dugard was kidnapped in 1991. She has also been arrested.

The Garridos had been living on a property in Antioch, Calif., a city about 275 kilometres away from the South Lake Tahoe home where Dugard was snatched.

Neighbour Diane Doty said she could often hear children playing in the Garridos' backyard, and she thought their children might have been living outside in tents. But she said her husband advised her not to get too nosy with the Garridos.

"I asked my husband, 'Why is he living in tents?'" she said. "And he said, 'Maybe that is how they like to live.'"