WASHINGTON (AP) — The Justice Department secretly obtained two months of telephone records of reporters and editors of The Associated Press in what the news cooperative’s top executive called a “massive and unprecedented intrusion” into how news organizations gather the news.

The records obtained by the Justice Department listed outgoing calls for the work and personal phone numbers of individual reporters, for general AP office numbers in New York, Washington and Hartford, Conn., and for the main number for the AP in the House of Representatives press gallery, according to attorneys for the AP. It was not clear if the records also included incoming calls or the duration of the calls.

In all, the government seized the records for more than 20 separate telephone lines assigned to AP and its journalists in April and May of 2012. The exact number of journalists who used the phone lines during that period is unknown but more than 100 journalists work in the offices where phone records were targeted on a wide array of stories about government and other matters.

In a letter of protest sent to Attorney General Eric Holder on Monday, AP President and Chief Executive Officer Gary Pruitt said the government sought and obtained information far beyond anything that could be justified by any specific investigation. He demanded the return of the phone records and destruction of all copies.

“There can be no possible justification for such an overbroad collection of the telephone communications of The Associated Press and its reporters. These records potentially reveal communications with confidential sources across all of the newsgathering activities

undertaken by the AP during a two-month period, provide a road map to AP’s newsgathering operations and disclose information about AP’s activities and operations that the government has no conceivable right to know,” Pruitt said.

The government would not say why it sought the records. Officials have previously said in public testimony that the U.S. attorney in Washington is conducting a criminal investigation into who may have provided information contained in a May 7, 2012, AP story about a foiled terror plot. The story disclosed details of a CIA operation in Yemen that stopped an al-Qaida plot in the spring of 2012 to detonate a bomb on an airplane bound for the United States.

Prosecutors have sought phone records from reporters before but the seizure of records from such a wide array of AP offices, including general AP switchboards numbers and an office-wide shared fax line, is unusual.

In the letter notifying the AP, which was received Friday, the Justice

Department offered no explanation for the seizure, according to Pruitt’s letter and attorneys for the AP. The records were presumably obtained from phone companies earlier this year although the government letter did not explain that. None of the information provided by the government to the AP suggested the actual phone conversations were monitored.

Among those whose phone numbers were obtained were five reporters and an editor who were involved in the May 7, 2012, story. The Obama administration has aggressively investigated disclosures of classified information to the media and has brought six cases against people suspected of providing classified information, more than under all previous presidents combined.

Rules published by the Justice Department require that subpoenas of records of news organizations must be personally approved by the attorney general but it was not known if that happened in this case.

The Justice Department lays out strict rules for efforts to get phone records from news organizations. A subpoena can be considered only after “all reasonable attempts” have been made to get the same information from other sources, the rules say. It was unclear what other steps, in total, the Justice Department might have taken to get information in the case.

A subpoena to the media must be “as narrowly drawn as possible” and “should be directed at relevant information regarding a limited subject matter and should cover a reasonably limited time period,” according to the rules.

It is unknown whether a judge or a grand jury signed off on the subpoenas.

The May 7, 2012, AP story that disclosed details of the CIA operation in Yemen to stop an airliner bomb plot occurred around the first anniversary of the May 2, 2011, killing of Osama bin Laden.

The plot was significant both because of its seriousness and also because the White House previously had told the public it had “no credible information that terrorist organizations, including al-Qaida, are plotting attacks in the U.S. to coincide with the anniversary of bin Laden’s death.”

The AP delayed reporting the story at the request of government officials who said it would jeopardize national security. Once officials said those concerns were allayed, the AP disclosed the plot, though the Obama administration continued to request that the story be held until the administration could make an official announcement.

The May 7 story was written by reporters Matt Apuzzo and Adam Goldman with contributions from reporters Kimberly Dozier, Eileen Sullivan and Alan Fram. They and their editor, Ted Bridis, were among the journalists whose April-May 2012 phone records were seized by the government.