Washington ? The White House began shipping documents Wednesday to the FBI for its CIA leak investigation after screening the material, a concern for some constitutional experts who say that gives the Bush administration room to withhold information.

Some 2,000 White House employees were asked to turn over telephone records, notes, correspondence, diary entries and other information that might help the FBI learn who leaked the identity of undercover CIA operations officer Valerie Plame.

Investigators already have interviewed Plame, the wife of former Ambassador Joseph C. Wilson, who publicly questioned Bush’s claim that Iraq had tried to buy uranium in Africa.

“We are moving as quickly as we can to get the information to the Justice Department,” White House press secretary McClellan said Wednesday evening.

Earlier, he said the counsel’s office was screening the documents to make sure that what is sent to FBI headquarters is “responsive” and “relevant” to the Justice Department’s request.

Constitutional lawyers say the counsel’s office is engaging in a fairly standard practice, but they worry about the administration’s penchant for secrecy will prompt them to withhold documents under the guise of public or national security interests.

Steven Aftergood, who directs the Federation of American Scientists’ government secrecy project, said the process “may create opportunities for mischief.”

“Any processing of materials before they are delivered to the Justice Department is awkward at the least,” he said.

“It’s important at this point to establish the integrity of the process, and this process raises questions, at least from a distance,” Aftergood said. “One has to wonder what might be withheld and why and who is supervising the vetting process.”

McClellan says it was too early to talk about whether the administration would assert executive privilege to withhold materials from investigators. White House officials declined to answer questions about whether the counsel’s office was flagging information before it was sent to the FBI, in case the administration later wanted to assert executive privilege.

“The role that the counsel’s office is playing is one of assisting the Department of Justice to get to the bottom of this because no one has more of an interest in getting to the bottom of this than the White House does, than the president does,” McClellan said.