It would violate people's privacy to publicly release raw data collected by automated license plate readers that police use to determine whether vehicles are linked to crime, but there may be ways to make the information anonymous that would require it to be disclosed, the California Supreme Court said Thursday.

The ruling came in a lawsuit by the American Civil Liberties Union and Electronic Frontier Foundation that sought a week's worth of license plate data — millions of records — from the Los Angeles County Sheriff's Department and Los Angeles Police Department to "understand and educate the public on the risks to privacy posed" by license plate readers in the area.

A unanimous Supreme Court ordered a lower court to consider methods to make the data anonymous and determine whether any of those efforts would require its release.

Jennifer Lehman, assistant county counsel for Los Angeles County, said in a statement that the county was "concerned that even making the information anonymous could pose unique and unintended problems."

She said it would raise those concerns in detail when the case is heard again by the lower court.

A message to the Los Angeles city attorney was not immediately returned.

Law enforcement agencies nationwide are using license plate readers attached to patrol cars and objects such as traffic signals. The devices indiscriminately capture images of license plates that come into view. The information is passed through databases to instantly check whether the car or driver has been linked to crime.

Officials say the scans are useful in tracking stolen vehicles, missing children and people wanted by police. For instance, authorities chasing a suspect in a fatal shooting at Delta State University in Mississippi in 2015 used an automatic license plate reader to track the man as he traveled across state lines.

Privacy advocates say the systems overwhelmingly capture innocent drivers, recording information about their locations that could be used to track their habits and whereabouts.