Police cruiser-mounted surveillance cameras are intended to scan license plates to detect drivers with outstanding warrants and stolen or unregistered vehicles, but if they're used for other purposes they could be violating privacy rights, according to the American Civil Liberties Union.

And the ACLU is looking to find out if that's happening. The organization submitted a lawsuit in U.S. District Court in Boston, requesting under the Freedom of Information Act that national law enforcement organizations turn over their records on information collected by the cameras, known as Automatic License Plate Readers.

"As ALPRs increasingly blanket American roads and highways, they raise the prospect of pervasive and prolonged surveillance of Americans' movements, a problem exacerbated when law enforcement agencies keep data about people not suspected of wrongdoing, and when data from discrete ALPR systems is pooled together into state, regional and even national databases."

The request was previously sent as a letter to the Department of Justice, FBI, DEA and other federal agencies in July; the lawsuit was filed Sept. 25. It seeks to obtain records of the type of data collected and stored by the cameras and records regarding the development or implementation of any federal database from the cameras.

The Medford Police Department has had a cruiser equipped with two license plate-reading cameras mounted to its trunk since 2009. It received the cameras through a federal grant funded by the American Recovery and Reinvestment Act.