White House employees have been given a Tuesday deadline to hand over any documents that might help the investigation into claims they illegally blew the cover of a CIA agent.
Questions are being asked about the failure to find any Iraqi weapons
In a memo, President George W Bush's legal adviser Alberto Gonzales urges staff to turn in records such as e-mails, computer records, notes and calendar entries.
A similar order has been sent by the Justice Department to the State and Defence Departments - as the investigation widens into who leaked the name of the agent - the wife of a former US diplomat - in revenge for his claims that intelligence officials exaggerated the case for war in Iraq.
President Bush has welcomed the investigation and his spokesman said on Friday he wanted to "get to the bottom of this, the sooner the better".
Disclosing a covert agent's name is a criminal offence in the US, punishable by up to 10 years in prison.
Correspondents say it is extremely rare for the department of justice to conduct a full investigation into the alleged leaking of classified information.
White House staff are to hand over relevant information by 1700 next Tuesday (2100 GMT).
Employees also must sign a certification form saying they have turned in materials or do not have any items related to the investigation.
This follows a decision by the justice department to widen the inquiry - from what started out as a preliminary investigation.
"We have received another letter from the Department of Justice. This letter requests the production of certain materials," White House spokesman Scott McClellan told reporters.
Mr McClellan said President Bush had "directed everyone to co-operate fully" with the investigation.
Secretary of State Colin Powell also said his staff had been asked "to make ourselves available".
"We have been asked to take a look at calendars and documents and see if we have any information that is relevant to this inquiry," Mr Powell said.
Act of revenge?
The allegations centre around the naming of Valerie Plame, wife of Joseph Wilson, the former US charge d'affaires in Baghdad.
Before the war in Iraq, Mr Wilson was sent by the CIA to the West African state of Niger in order to investigate claims that Iraq had tried to buy nuclear material there.
His report concluded that there was no evidence for the claims.
Despite this, Mr Bush referred to them in his State of the Union address in January.
In a subsequent article in the New York Times, Mr Wilson questioned why his report had been ignored.
Bush's policies on Iraq are coming under closer scrutiny
The White House later admitted it had been a mistake to include the claim in the address.
A week after Mr Wilson's article appeared, Valerie Plame was exposed by journalist Robert Novak, who said he based his report on two unidentified senior administration officials.
A report in the Washington Post newspaper has suggested that White House officials blew the cover of Mr Wilson's wife in order to discredit him, by suggesting he had been given the Niger mission only at her urging.