Losing Track of Sex Offenders

It's been almost three weeks since 7-year-old Somer Thompson was abducted in Orange Park, Fla., her body found in a Georgia landfill. Authorities now are questioning sex offenders in the community. There are 159 registered offenders in a 5-mile radius of Somer's hometown.

"That's your biggest fear, that your child is going to be missing or they're going to die," said Carol Jones, a resident.

That number of sex offenders in one Florida town is not unusual. There are almost 700,000 registered sex offenders in the United States: more than 51,000 in Florida; 57,000 in Texas; more than 117,000 in California, reports CBS News correspondent Bill Whitaker.

In Antioch, California where kidnap victim Jaycee Dugard was held in a backyard for 18 years, allegedly by convicted rapist Phillip Garrido, there are 92 registered sex offenders just in Garrido's zip code.

Those numbers have prompted states and cities across the country to pass laws restricting where sex offenders can live. Jessica's Law here in California prohibits sex offenders from living within 2,000 feet of a park or a school - places children congregate.

Similar restrictions in other states are forcing sex offenders to cluster in isolated areas - like this encampment under a Miami freeway. Parole officer Mauricio Lopez monitors 20 high-risk sex offenders in one Pasadena, California neighborhood. Neighbors are fearful.

"We have neighbors who do not allow their children to ride their bikes or get out of the house at all," said one resident.

Authorities have lost track of some 100,000 sex offenders. Critics say better tracking, not isolation, is the answer.

"The most dangerous sex offenders are highly mobile, so they will travel, they'll move from community to community, they will seek out opportunities," said Ernie Allen with the National Center for Missing and Exploited Children.

Next year all states will be required by federal law to closely track all sex offenders and to inform the public who are the most violent.