The Detroit Public School system is launching a new security system designed to keep sex offenders out of the city's schools.

The system works by running instant background checks against sex offender registries and then issuing ID badges that identify which area of a school a person is allowed to enter. Anyone who doesn't pass the background check will not be allowed access to the school. Officials say the system will not check any other criminal databases.

The system can scan driver licenses and ID cards. It can also run checks using a visitor's name and date of birth.

The ID badges that are issued by the system include the person's name and picture. They are temporary and expire after a day. Contractors, regular volunteers and frequent visitors can be issued long-term badges.

District officials say the system is already in place at some locations, including Martin Luther King Jr. Senior High School. They say it has already identified a registered sex offender who left the property without incident after he was denied entry to the building.

Officials are initially rolling out the system at 33 sites, which include all of the city's high schools, career technical schools and the district's new Police Command center. It will eventually be put into place at all of the district's schools.

A similar system, issuing ID cards to students, is already in place at the city's high schools. That system issues badges color-coded by school, allowing security personnel to instantly identify which students belong on campus.