ST. PAUL, Minn. (AP) — They're on squad cars and street lights, and they track where you're driving. Across Minnesota, police and sheriffs have been using automated license plate readers for years to find stolen cars and aid investigations.

Their spreading use and questions of data security, fueled by recent breaches of statewide databases, has focused attention on the lack of regulation. Until the data was temporarily classified late last year, anyone could ask police for a list of when and where a car had been spotted.

Lawmakers will soon consider restrictions on the data stored via the readers, with Rep. Mary Liz Holberg, R-Lakeville, saying she plans to introduce a bill in the next few weeks.

There's little question the Legislature will restrict public access to police's license plate databases. The bigger question will be: How long should police be able to keep tracking information on law-abiding Minnesotans?

Holberg said the law needs to balance the concerns of police, who say keeping the data longer is valuable. Other advocates and lawmakers say tracking citizens for any length of time violates civil liberties.

"I really think that there needs to be a full vetting from law enforcement for why they need to hang on to this," said Rep. John Lesch, a St. Paul Democrat and chairman of the House Civil Law Committee.

Most license plate readers are mounted on squad cars, automatically scanning plates every minute on Minnesota roads. The system checks each against a statewide crime database, and the officer gets an alert when there's a "hit" for a wanted vehicle.

There at least 25 readers in Minnesota, but the precise number is unclear because no state agency keeps track of them. Jim Franklin, executive director of the Minnesota Sheriffs' Association, said they're primarily used in urban Minnesota.

"But like any technology, sooner or later it will move into some sort of an application in the rural areas," Franklin said.

Minneapolis police have about 10 readers; St. Paul police have seven. There are five in Bloomington, two in Duluth and more in Lakeville, Roseville, Maplewood and Washington and Olmsted counties. The Minnesota State Patrol has one.

Almost $4 million in grants from the Minnesota Department of Commerce last April helped police departments and sheriff's offices buy readers, billing it primarily as a tool to fight auto theft.

The readers also feed their scans into their agency's database, which officers can search to find when and where a car has been seen.

That's the investigative feature police will be fighting for at the Capitol. The longer the data can be kept, police reason, the farther back they can go to track someone down.

So far law enforcement agencies have set their own rules.

Minneapolis police kept it for up to a year until last fall, when it cut the retention period to 90 days. Around the same time, St. Paul bumped its retention period up from two weeks to 90 days. The State Patrol tosses the data from its sole reader after just 48 hours.

Franklin said it will be good to have a standard for all law enforcement to follow. He said they could live with a 180-day maximum retention period as a compromise.

But state lawmakers have a much shorter period in mind.

Lesch, whose committee will hear the bill first, said he thinks any license plate data that's not a "hit" should be immediately tossed.

"There's no reason for them to be holding information about citizens for whom they do not have a reasonable suspicion of criminal activity or probable cause," he said. "That's not what we do in America."

Holberg, the bill's author, said she's waiting to hear arguments from police but she'll likely push for "an extremely short" retention period.

Bloomington Police Sgt. Mark Elliot said the short window lawmakers have in mind would wipe out any investigative power the database gives police. That's the case law enforcement will try to make when hearings start, with success stories from the longer retention period.

Chuck Samuelson, executive director of American Civil Liberties Union of Minnesota, said there should be a one- to two-day retention period, plus strict penalties for officers who improperly access the database and disclosure about where the readers are located.

"You cannot allow those things to be hidden by the government," he said.

Republican Rep. Tony Cornish and said it's "probably one of the few things in my life I've ever agreed with the ACLU on." Cornish, a peace officer for more than 30 years, Cornish said he would support no more than a 48-hour window when plates don't get an immediate hit.

All of the tracking data in the state has been under wraps since Minneapolis Mayor R.T. Rybak asked the state to reclassify it as non-public in December.

But before then, Minneapolis police's location data had been requested by people checking where their cars has been spotted; engineering students at Carnegie Mellon University and Dartmouth College looking for data analysis practice; and reporters, bloggers and data privacy advocates. One woman asked the police for information on her brother-in-law's plate to see if he was violating the terms of his work release program.

A work group set up to make recommendations to the Legislature on crime and justice issues suggested making all data from license plate readers private to keep sensitive information out of the wrong hands. Lesch and Cornish said they both support making it private.

Don Gemberling, a data privacy expert and member of the Minnesota Coalition on Government Information, said his group will ask the Legislature to keep the information public as a means to "know what the cops are doing."

"The further we go into the technology ... the more important we think it is that we all know what's happening to us," Gemberling said.

Copyright 2013 The Associated Press.