Nearly a third of the Arizona's high-risk, registered sex offenders were unaccounted for at some point during 2012, raising questions about the state's system of tracking and monitoring sex offenders, according to a new analysis by the Arizona Republic.

The newspaper's analysis of nearly 5,700 high-risk offender registrations found large concentrations of offenders in the central areas of Arizona's two largest cities.

About one-third of these high-risk offenders had an unverified address at some point during the seven months the Republic conducted its analysis, meaning authorities could not report precisely where they were and the state database did not have addresses for them.

Nonetheless, state law requires their registration to an address or "place of residence." So authorities have created an unsettling situation: permitting clusters of homeless offenders to register to central Phoenix and Tucson street corners.

Nearly 200 offenders were homeless statewide as of Nov. 7, many registered to street corners or intersections close to homeless shelters.

Though it is a potential crime for those convicted of dangerous crimes against children to live within 1,000 feet of schools and day-care centers, police working the streets struggle to discern whether offenders are complying with the distance restrictions.

To do so requires research on the nature of their offense - determining if the law classifies it as a dangerous crime against children - and whether the offenders' assigned risk levels prohibit their being at certain locations.

There is little political incentive or public pressure to change the current monitoring system or to dedicate taxpayer money to housing for a group of ex-cons viewed largely as social pariahs.

But state Sen. Leah Landrum Taylor, D-Phoenix, said the time to act is approaching.

"There's no choice but coming up with some way to ... monitor these individuals," Taylor, the incoming Senate minority leader, told the Arizona Republic. "There are a lot of things we have to address this coming session, and certainly this should be one."

David Bridge, managing director of the Human Services Campus, a central Phoenix nonprofit that helps reintegrate the homeless into society, said the practice of registering sex offenders to street corners benefits no one - not the public, not the offenders, and not the government agencies spending taxpayer money on short-term solutions.

"It's a time bomb," Bridge said.

Convicted sex offenders released from prison must register within 10 days, notifying the sheriff of the county and local police of the city where they plan to live. Those who move to a new address must re-register within 72 hours. That information is forwarded to the Arizona Department of Public Safety, which maintains a public sex-offenders database.

Offenders released into homelessness must comply with the requirement by providing a general description of the place where they plan to be transient. The location must be updated with the sheriff's office every three months.