SAN FRANCISCO (August 11, 2012)--Law enforcement agencies across the county are adding a new form of social media to their arsenal of crime fighting tools.

Almost 6,000 law enforcement agencies now use the public notification service Nixle to provide residents with real-time alerts on crimes in progress, traffic messes and missing children.

With the San Francisco-based service approaching 1 million subscribers and police departments participating in major cities such as Chicago, Los Angeles, Baltimore and Dallas, Nixle is part of what one expert calls a new "blue wave" of community policing that lets cops reach out directly to the public.

The International Association of Chiefs of Police said in a recent survey of 800 law enforcement agencies that nearly 90 percent of them use some form of social media.