By Mark Hosenball and Tabassum Zakaria
WASHINGTON (Reuters) - The Justice Department's controversial decision to seize phone records of Associated Press journalists was just one element in a sweeping U.S. government investigation into media leaks about a Yemen-based plot to bomb a U.S. airliner, government officials said on Wednesday.
The search for who leaked the information is being led by the U.S. Attorney's Office in Washington and has involved extensive FBI interviews of personnel at the Justice Department, U.S. intelligence agencies, the White House's National Security staff and the FBI itself.
The interviews have been lengthy and thorough, said people who have been questioned in the investigation, but requested anonymity. Two of those interviewed said leak inquiries were always aggressive and that being questioned is a wearing and unpleasant experience.
The investigation, which a law enforcement official has said was prompted by a May 7, 2012, AP story about the operation to foil the Yemen plot, appears to be ongoing. Some potential witnesses have been advised they are likely to be interviewed in the next two or three weeks.
Officials in the office of Ronald Machen, the U.S. attorney for the District of Columbia, could not immediately be reached for comment.
Attorney General Eric Holder, who recused himself from involvement in the case, largely sidestepped questions from angry lawmakers on Wednesday about his department's secret seizure of AP records, which the news agency revealed on Monday.
The seizure, denounced by critics as a gross intrusion into freedom of the press, has created an uproar in Washington and led to questions about how the Obama administration is balancing the need for national security with privacy rights.
There are signs the administration's efforts to find the alleged leaker were unproductive - at least before the Justice Department seized two months of records of phone calls by the AP and its journalists.
"Seeking toll records associated with media organizations is undertaken only after all other reasonable alternative investigative steps have been taken," Holder's deputy, James Cole, said in a letter on Tuesday to AP President Gary Pruitt, who has protested the government's action.
In that letter, Cole revealed the Justice Department had conducted more than 550 interviews and reviewed tens of thousands of documents before subpoenaing phone company records of AP calls.
Reuters was one of nearly 50 news organizations that signed a letter to Holder on Tuesday complaining about the AP phone record seizures.
Floyd Abrams, a prominent First Amendment and media attorney, said, "The breathtaking scope of these subpoenas served on the telephone companies might suggest that after all this time, they have no idea who they're looking for."
Another possibility is "they are touching all bases" because they suspect someone but are not sure, said Abrams, a partner at Cahill Gordon and Reindel LLP in New York. He said it was difficult for an outsider to know.
"I don't think that there is any doubt that this is a serious investigation that they have spent a lot of time on and that they feel deeply about," Abrams said. Justice's targeting of a large number of phone lines and the AP journalists who use them "taken together, certainly makes it look like the largest, most intrusive action by the government vis-a-vis the press that I can remember."
Holder has called the leak "very, very serious" and said it "put the American people at risk." He did not provide details.
The AP has reported that it delayed reporting the story of how the United States had foiled a plot by a suicide bomber affiliated with Yemen-based Al Qaeda in the Arabian Peninsula, or AQAP, at the request of government officials, who said it would jeopardize national security. Once U.S. officials said those concerns were allayed, the AP said, it disclosed the plot.
A law enforcement official said on Wednesday that because officials were so concerned and shocked by the leak, they opened an investigation into how the AP found out about the spy operation even before the news agency ran its initial story. The AP had contacted the government and asked for comment several days before the story was published.
The AP's first story reported the CIA had "thwarted an ambitious plot" by AQAP to attack an airline with a newly designed underwear bomb and said the FBI had acquired the bomb. The AP reported it did not know what had happened to the alleged bomber.
A few hours after the story was published, John Brennan, then chief White House counterterrorism adviser and now director of the CIA, held a conference call with former counterterrorism officials who frequently appear as TV commentators. Brennan said the plot was never a threat to the U.S. public or air safety because Washington had "inside control" over it.
That night, Richard Clarke, a former counterterrorism adviser to Presidents Bill Clinton and George W. Bush, suggested on ABC News there was a Western spy or double agent in on the plot. "The U.S. government is saying it never came close because they had insider information, insider control, which implies that they had somebody on the inside who wasn't going to let it happen," Clarke said.
The next day's headlines were filled with news of a U.S. spy planted inside AQAP who had acquired the latest, non-metallic model of the underwear bomb and handed it over to U.S. authorities.
Reuters subsequently reported that the spy inside AQAP had been recruited by British intelligence, principally the counterterrorism agency known as MI-5, that the informant had to be whisked to safety, and that UK authorities were deeply distressed that news of the operation had leaked.
During Senate consideration of his nomination to become CIA director, Brennan confirmed he had been interviewed by people investigating both the foiled bomb plot leak and another series of leaks related to alleged U.S. cyber warfare against Iran's nuclear program.
Brennan strongly denied he had leaked any sensitive or secret information to the media. Sources familiar with Brennan's conference call with the TV pundits said at least two of the former officials who were on the call with Brennan had not been contacted by leak investigators.
(Editing by Warren Strobel and Peter Cooney)