(CBS/AP) FBI demands to telecommunications companies went beyond requesting phone records of customers under suspicion to include analyses of their broader patterns of communication with others as well, newly obtained documents show.

The Federal Bureau of Investigation used national security letters to request information on the wider "community of interest" linked to individuals under suspicion, according to the documents.

The data-mining technique can lay bare phone and e-mail links that tie together otherwise indiscernible networks of individuals. Law enforcement officials value that sort of data as a means of identifying a suspect's potential conspirators. Privacy advocates say it can ensnare people with no tie to illegal or suspicious activity.

The "community of interest" requests were included in more than 2,500 pages of FBI documents the Electronic Frontier Foundation, a watchdog group, obtained through the Freedom of Information Act. The New York Times first reported on the requests in a story posted to its Web site Saturday.

Marcia Hofmann, a lawyer for the group, told the Times, “This whole concept of tracking someone’s community of interest is not part of any established F.B.I. authority. It’s being defined by the F.B.I. And when it’s left up to the F.B.I. to decide what information is relevant to their investigations, they can vacuum up almost anything they want.”

The FBI letters use boilerplate language to request companies provide calling records for redacted lists of telephone numbers, citing "exigent circumstances." An Aug. 9, 2005, letter and others from that year also include the following: "Additionally, please provide a community of interest for the telephone numbers in the attached list."

Earlier this year, the Justice Department's inspector general uncovered 700 cases in which FBI agents obtained telephone records through such "exigent letters," which asserted that grand jury subpoenas had been requested for the data when in fact such subpoenas never had been sought. The FBI eliminated use of the letters earlier this year.

The FBI recently stopped asking for "community of interest" data, amid broader questions about the bureau's aggressive use of national security letters, government officials told The Times.

A federal judge struck down a key part of the USA Patriot Act anti-terrorism laws on Thursday, saying the FBI must justify to a court the need for secrecy if the orders to hand over phone and e-mail records will last longer than a reasonable and brief period of time.

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