How Nuclear Secrets Disappeared

A chronology of events involving the disappearance of two computer hard drives containing nuclear secrets from a vault at the Los Alamos National Laboratory, according to Energy Department officials.

April 7: A member of an emergency nuclear response, or NEST, team recalls seeing the hard drives in the vault during an inventory.

April 27: Another member of the response team does not recall seeing the two drives, contained in one of three emergency response ''kits'' in the vault, but says if they had been missing he would have taken notice.

May 2-4: The NEST emergency response team participates in an exercise at the Lawrence Livermore weapons lab in California. It's not known whether ''Kit No. 2'' -- later to be found with the drives missing -- was used in the exercise.

May 4: A wildfire begins in federal parkland near the Los Alamos laboratory and quickly spreads out of control.

May 7: With the laboratory threatened by the fire, members of the NEST team late in the evening inspect the vault to assure the three kits are ''out of harm's way'' and discover the two drives missing from Kit No. 2. The discovery is not reported.

May 8: The Los Alamos lab is evacuated because of the fire threat and scientists disperse.

May 22: With the fire danger over, operations resume at the lab.

May 24: A group of scientists begin an ''intense search'' for the missing hard drives, but senior lab officials are not informed of the possible loss.

May 31: Los Alamos lab director John Browne first learns of the missing hard drives and the next day informs Energy Department officials in Washington.

June 1-2: Air Force Gen. Eugene Habiger, the DOE's top security official, and Edward Curran, chief of counterintelligence, are informed of the loss and meet with the FBI.

June 4: A team of 22 FBI agents and a dozen DOE investigators, led by Habiger, descend on Los Alamos and begin investigation, interviewing those with access to the vault and continuing the search.

June 12: The Los Alamos laboratory announces in a news release that two top-secret hard drives containing nuclear data had been found missing.

June 13: Six laboratory managers, including the head of the nuclear weapons programs, are put on paid leave, pending the investigations. Richardson complains about not being informed about the loss for nearly three weeks and promises disciplinary action.

June 14: Congressional intelligence and armed services committees begin hearings into the security breakdown. At Los Alamos, FBI and DOE officials begin plans to give polygraph tests to scientists who had access to the vault.