MARIETTA, Ga. (AP) — Police in two Cobb County jurisdictions say they've used federal grant money to install automatic license plate readers they use to scan and store hundreds of car tags in a database.

The Marietta Daily Journal  reported Thursday that Marietta and Acworth police are among departments across the country that are using automatic license plate readers.

Acworth Police Capt. Mark Cheatham and Marietta police spokesman David Baldwin said each of their departments are using two automatic license plate readers to quickly identify and store license plate information.

The readers snap a photo of a car, its license plate, the date, time, and location where the car was spotted, Cheatham said. The readers also scan databases by plugging in the car's tag number and feeding officers information on whether the car is associated with a crime anywhere in the country.

Police say the readers are effective despite concerns over privacy, and law enforcement only uses the stored information if it's traced back to criminal activity.

"Two weeks ago, we located a stolen car and made an arrest off that case by using this technology," Cheatham said. "The camera system stores all the photos but we'll never even know we have a picture of your tag if you haven't committed a crime. Unless we have a reason to suspect, we'll never know."

Baldwin said police in his department have used the readers for a variety of reasons.

"We've gotten everything from the minor traffic violations, such as someone driving with a suspended license, to a wanted person to a stolen car."

Despite the technology being widely embraced by law enforcement, the American Civil Liberties Union issued a report earlier this week saying the systems are tracking law abiding citizens as well as criminals, and that the data shouldn't be stored indefinitely by police.

An article on the organization's website says ACLU affiliates in 38 states and the District of Columbia asked nearly 600 federal state and local law enforcement agencies how they use the readers.

Representatives from the organization say few law enforcement agencies have explicit rules on how the automatic license plate readers can be used.

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