WASHINGTON (AP) — Police across the country may be intercepting phone calls or text messages to find suspects using a technology tool known as Stingray. But they're refusing to turn over details about its use or heavily censoring files when they do.

Police say Stingray, a suitcase-size device that pretends it's a cell tower, is useful for catching criminals, but that's about all they'll say.

For example, they won't disclose details about contracts with the device's manufacturer, Harris Corp., insisting they are protecting both police tactics and commercial secrets. The secrecy — at times imposed by nondisclosure agreements signed by police — is pitting obligations under private contracts against government transparency laws.

Even in states with strong open records laws, including Florida and Arizona, little is known about police use of Stingray and any rules governing it.

A Stingray device tricks all cellphones in an area into electronically identifying themselves and transmitting data to police rather than the nearest phone company's tower. Because documents about Stingrays are regularly censored, it's not immediately clear what information the devices could capture, such as the contents of phone conversations and text messages, what they routinely do capture based on how they're configured or how often they might be used.

In one of the rare court cases involving the device, the FBI acknowledged in 2011 that so-called cell site simulator technology affects innocent users in the area where it's operated, not just a suspect police are seeking.

Earlier this month, journalist Beau Hodai and the American Civil Liberties Union of Arizona sued the Tucson Police Department, alleging in court documents that police didn't comply with the state's public-records law because they did not fully disclose Stingray-related records and allowed Harris Corp. to dictate what information could be made public.

Revelations about surveillance programs run by the federal National Security Agency have driven a sustained debate since last summer on the balance between privacy and government intrusion. Classified NSA documents, leaked to news organizations, showed the NSA was collecting telephone records, emails and video chats of millions of Americans who were not suspected of crimes.

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That debate has extended to state and local governments. News organizations in Palm Springs, Calif.; Tallahassee, Fla.; Sacramento, Calif., and Pittsburgh are among those that have been denied records about Stingrays or Stingray-like devices, including details of contracts that Harris has with government agencies.

In a response to a records request from the Tallahassee Democrat newspaper about Florida's use of cell-tracking technology, the state's top police agency provided a four-page, heavily censored document signed by a police investigator. The newspaper reported that the document referred to guidelines concerning the purchase of items and sought the department's agreement to the "provisions/content of the Non-Disclosure Agreement."

The Desert Sun of Palm Springs made a similar request to the San Bernardino County Sheriff's Department, which said it had to maintain secrecy even though the newspaper found information online about cell site simulators.

And in Sacramento, the local sheriff's office told a TV station it would "be inappropriate for us to comment about any agency that may be using the technology" in light of a Harris nondisclosure agreement.

Many of the requests were part of an effort to investigate the devices by Gannett Co. Inc., which publishes USA Today and owns other newspapers and television stations around the country.

"I don't see how public agencies can make up an agreement with a private company that breaks state law," said David Cuillier, the director of the University of Arizona's journalism school and a national expert on public-records laws. "We can't have the commercial sector running our governments for us. These public agencies need to be forthright and transparent."

A representative for Melbourne, Fla.-based Harris Corp. declined to comment or elaborate on how the company's agreements comport with open records laws. Court documents in Hodai's case show Harris' agreement required the Tucson city government not to "discuss, publish, release or disclose any information" about its products without the company's written consent.

The agreement also required the city to contact Harris when it receives public-records requests about a "protected product," like a Stingray, so that the company can "challenge any such request in court." The police department declined to comment on Hodai's lawsuit.

He had sought Harris contracts and police emails about how the technology is used. Email records show a Harris contract manager advised a Tucson police sergeant on what records couldn't be released to the public; the manager relied on the U.S. Freedom of Information Act, which governs records of the executive branch of the federal government.

Nathan Freed Wessler, a staff attorney with the ACLU, said there's often a distinction in public-records laws to protect bona fide trade secrets — such as circuit board diagrams — as opposed to broader information like agency policies governing a Stingray's use or purchase agreements. He said police in Florida have declined to tell judges about the use of Stingrays because of nondisclosure agreements.

A December 2013 investigation by USA Today found roughly 1 in 4 law enforcement agencies it surveyed had performed tower dumps, and slightly fewer owned a Stingray. But the report also said 36 additional agencies refused to provide details on their use, with most denying the newspaper's public-records requests.

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Follow Jack Gillum on Twitter at http://twitter.com/jackgillum

Sunshine Week, promoting the importance of access to public information, runs from March 16-22