A senior Justice Department official, speaking on condition of anonymity, said those agencies, and possibly others, could get letters urging officials to preserve documents such as phone logs and not to delete e-mails. Similar letters have already gone to the White House and CIA.
Defense Department officials confirmed Thursday they were told to expect such a letter. At the State Department, spokeswoman Susan Pittman said she did not know if a letter had been received but that the agency "would cooperate fully" if asked.
Preventing loss of evidence is a key piece of the early stage of the FBI's investigation, which is focused at the outset on narrowing the list of government officials who may have known the CIA officer's identity.
White House spokesman Scott McClellan told reporters Thursday that the White House had not received any subpoenas in the investigation and that, to his knowledge, no staffers had been interviewed by the FBI.
The FBI has assembled a team of about a half-dozen experienced agents to handle the investigation into who leaked the name of a CIA officer married to former Ambassador Joseph C. Wilson. Wilson had accused the Bush administration of manipulating intelligence to exaggerate the threat posed by Iraq.
The officer's name, Valerie Plame, first appeared in a July 14 story by syndicated columnist Robert Novak, and she was identified later by Newsday as an undercover officer.
In Congress, Democrats and Republicans sparred over whether a special counsel should be appointed to investigate. Democrats contend an agency headed by Bush appointees cannot adequately investigate the administration.
"If there ever was a case for the appointment of a special counsel, this is it," said California Rep. Nancy Pelosi, the House Democratic leader.
Republicans like Senate Majority Leader Bill Frist dismissed those concerns.
"I know there are a lot of calls for other ways to address it from Democrats. They have a partisan flavor to them so they are to be expected. I have confidence in our Department of Justice and FBI to handle this appropriately," said Frist, R-Tenn..
Overseeing the investigation is John Dion, a 30-year career prosecutor who has headed the counterespionage section at the Justice Department since 2002. FBI agents from the counterintelligence and inspections division and from the Washington field office will do the legwork.
The FBI, which can use grand jury subpoenas to compel disclosure of any evidence, has regularly used polygraph tests in investigations involving classified information. Asked Wednesday if White House staff members would submit to lie detector tests if requested, McClellan called the question "hypothetical."
"We will cooperate fully with the investigation and make sure that we preserve the integrity of the investigation," he said.
The White House and the Republican National Committee turned up the heat Wednesday on Wilson. The GOP's communication office highlighted remarks in which Wilson backtracked from his original assertion that Karl Rove, Bush's chief political strategist, was responsible for the leak.
McClellan told reporters that Wilson "has said a lot of things and then backed away from what he said. So I think part of your role is to do some further questioning there."
McClellan also said there were some people looking for partisan political advantage in the leak investigation. He didn't mention names but said they're trying to "sensationalize" the matter for political gain.
Novak, in a column published Wednesday, wrote that he discovered Plame's identity when talking with a senior administration official about why Wilson, who had been part of President Clinton's National Security Council, had been chosen to investigate allegations that Iraq tried to buy uranium from Niger.
A second official confirmed that Wilson's wife was a CIA officer, Novak wrote, adding that the CIA itself never suggested to him that publication of her name would endanger anyone. Novak also wrote that the officer's identity was widely known in Washington.
Former Attorney General Janet Reno, in June 2000 testimony before the Senate Intelligence Committee, said the pool of potential leakers in any administration is so big it makes most leak investigations impractical.
"Almost all leak investigations are closed without having identified a suspect," she said.
Justice Department guidelines allow for journalists to be subpoenaed only on rare occasions, after all reasonable attempts are made to obtain the information from other sources.
Newsday Editor Howard Schneider said the newspaper had not been contacted by the Justice Department and that its reporters were continuing to pursue the leak story.
An ABC-Washington Post poll found 69 percent of Americans, including 52 percent of Republicans, believe a special counsel should be appointed. A substantial majority, 72 percent, said it's likely that someone in the White House leaked the classified information, but only 34 percent think it's likely Bush knew about the leak beforehand.