Six cities across the state, plus the Connecticut State Police, were the targets Wednesday of an effort to gauge the extent that law enforcement may be using cellphone locations to invade privacy.

The American Civil Liberties Union of Connecticut joined other ACLU offices in a nationwide campaign to determine whether police are improperly tracking people using their cellphone data. It's one of the first efforts at protecting digital privacy.

Freedom of Information Act requests were sent to the state police and local police departments of Danbury, Waterbury, New Haven, Willimantic, New London and Berlin in what could be the start of a multiyear effort to determine whether privacy rights have been violated.

Except for Berlin, where a warrantless federal tracking campaign occurred in 2008, the cities were selected geographically.

The ACLU asked whether law enforcement officials show probable cause and obtain warrants from judges before obtaining cellphone location information; and how often they seek such information.

In addition, the ACLU requested budget totals on the cost of local cellphone tracking; and policies and procedures for gathering location data.

David McGuire, staff attorney for the ACLU of Connecticut, said that although Connecticut is relatively small, there are varying police cultures.

"We tried to pick departments that had some substantial activity and were widely dispersed," said McGuire, adding that similar requests occurred Wednesday in 30 other states. "Nationwide it is a large problem and innocent people are being caught in these cellphone dragnets. We're trying to understand the magnitude of the problem."

Danbury Police Chief Alan Baker confirmed the ACLU request made under the state's Freedom of Information Act.

"We did receive the request and like all FOI requests, it has been referred to corporation counsel for review," Baker said. "We anticipate it will take between 30 and 45 days to comply, which is standard. It's an emerging area of the law, and I don't know how much documentation we might have on it."

Lt. J. Paul Vance, spokesman for the state police, confirmed in a Wednesday phone interview that the state Department of Public Safety utilizes cellphone data. "We might use cellphone records depending on the investigation and what's required," Vance said. "We use cellphone records and sometimes it's helpful in criminal investigations. We don't use cellphone information for anything more than criminal investigations. We can and do obtain search warrants as required. It's not our intent to trample on anyone's rights."

McGuire said that the current requests for information were not given to the FBI because local police are the focus of this initial research effort.

In 2008, federal agents got details on calls to and from 180 mobile phones serviced by nine carriers, including the locations of the phones, in what amounted to an act of "mass surveillance," in Berlin, a southern suburb of Hartford, he said.

"This is very much the same as the government walking into private homes on a fishing expedition, without a warrant, and searching the premises," McGuire said. "And technology has made it a whole lot easier. These people were subjected to an unconstitutional search and never even knew it. If any law enforcement agencies in the state are carrying out similar intrusions, the public should know about it."

The ACLU said that more than 375 requests in 31 states were made by 34 ACLU affiliates to delve into the secret use of mobile phone-tracking capabilities.

"The ability to access cellphone location data is an incredibly powerful tool and its use is shrouded in secrecy. The public has a right to know how and under what circumstances their location information is being accessed by the government," said Catherine Crump, staff attorney for the national ACLU Speech, Privacy and Technology Project, in a statement. "A detailed history of someone's movements is extremely personal and is the kind of information the Constitution protects."

"The Constitution guarantees Americans freedom from unwarranted government intrusion everywhere -- in their homes, online and on their cellphones," said Andrew Schneider, executive director of the ACLU of Connecticut. "Technology may make it easier for that intrusion to happen, but that's no excuse for it."

More information about the ACLU requests is available at: acluct.org/celltrack.

Staff Writer John Pirro contributed to this report.