The FBI is investigating Clinton administration national security adviser Samuel R. "Sandy" Berger's removal of classified documents from the National Archives, attorneys for Berger confirmed last night.

Berger inadvertently took copies of several versions of an after-action memo on the millennium bombing plot from the Archives last fall, said his attorney Lanny Breuer. The lawyer said one or more of the copies were then inadvertently discarded.

The inspector general of the Archives began an investigation last October and turned it over to the FBI in January. FBI agents searched Berger's office and home safe, and the probe is continuing, Breuer said.

Berger spent three days at the Archives, on Pennsylvania Avenue NW, last summer and fall examining documents to provide the Clinton administration's responses to inquiries from the presidential commission investigating the Sept. 11, 2001, terrorist attacks. The commission's final report is slated for release Thursday.

"There was huge pressure to review the documents quickly for claims of executive privilege and responsiveness," Breuer said. Berger reviewed copies of thousands of documents on July 18, Sept. 2 and Oct. 2, 2003, Breuer said. Later in October, the Archives notified Berger that documents were missing.

Berger discovered several versions of the classified memo in a leather portfolio he had taken to the Archives, his attorney said. He returned them and papers on which he had taken notes about materials he had reviewed. Those notes, Breuer said, were not supposed to have been removed from the Archives without review by employees there. Berger's actions, said Breuer, were the result of "sloppiness" and were unintentional.

One or more missing versions of the 15-page memo could not be located among Berger's possessions, and he thinks he probably discarded the papers, Breuer said.

Breuer said FBI agents have not interviewed Berger, although he has offered to cooperate. Breuer said agents did not take anything from Berger's safe, and took from his office a few index cards bearing notes from meetings on the Middle East that Berger made at Camp David.

One Sept. 11 commission member reached last night was not aware of the Berger investigation. A senior commission official said the panel has no comment on the probe.

The commission's staff was told in general about the investigation but did not view the documents as crucial, said sources close to the issue who declined to be identified because of the criminal investigation.

The Associated Press first reported late yesterday that the FBI was looking into Berger's handling of classified documents. Federal laws prohibit unauthorized release or removal of classified documents.

Breuer said the Justice Department and the FBI have informed him that Berger is the subject of a criminal probe but not a target.

In his testimony before the Sept. 11 commission in March, Berger said he had ordered the after-action review of the millennium threat and that the report contained 29 recommendations, most of which were implemented subject to funding. He also testified that the review led President Bill Clinton to request $300 million from Congress, primarily for domestic security programs, and to reallocate $79 million within the CIA's budget to counterterrorism.

The missing copies, according to Breuer and their author, Richard A. Clarke, the counterterrorism chief in the Clinton administration and early in President Bush's administration, were versions of after-action reports recommending changes following threats of terrorism as 1999 turned to 2000. Clarke said he prepared about two dozen ideas for countering terrorist threats. The recommendations were circulated among Cabinet agencies, and various versions of the memo contained additions and refinements, Clarke said last night.

Breuer said that Clarke had prepared a "tough review" and that the document was something of a critical assessment of what agencies did well and what they failed to do in the face of the millennium threat.

Clarke said it is illogical to assume Berger would have sought to hide versions of the memo, because "everybody in town had copies of these things." He said he could not recall most of the recommendations, but one that he did remember -- having FBI field offices send wiretap material to Washington for translation instead of translating it locally -- still has not been accomplished.

National security adviser Condoleezza Rice testified to the Sept. 11 panel that she did not recall being briefed on the report during the transition period to the Bush administration, and she said she did not read it until after the Sept. 11 attacks, when Vice President Cheney distributed it.

Rice characterized the report as concluding that Ahmed Ressam, later convicted in a plan to blow up Los Angeles International Airport, was caught by chance. "I think it actually wasn't by chance, which was Washington's view of it," Rice testified. "It was because a very alert customs agent" who was suspicious of Ressam as he attempted to cross into Washington state from Canada, she said.

Researcher Karl Evanzz contributed to this report.

His lawyer said that Samuel "Sandy" Berger's removal of classified papers was accidental.