Rickey R. Hass, deputy inspector general for audits and inspections at the Energy Department, said in the report that outside contractors had made changes to one system meant to monitor nuclear explosions without first getting approval from the proper federal officials.

That and other site-level problems have persisted in part because the government hasn't ensured that changes to its information systems are in line with potential risks, the department's internal watchdog's office said.

"Without improvements, the weaknesses identified may limit program and site-level officials' ability to make informed risk-based decisions that support the protection of classified information and the systems on which it resides," the audit concluded.

No classified information was compromised, said Damien LaVera, a spokesman for the Energy Department's National Nuclear Security Administration, which operates the labs.

In a written response to the inspector general, a top ranking administration official said the paper-based compliance review did not factor in the lab's additional strategies to counter a constantly changing set of threats.

"We do not believe conclusions documented in this report can be extrapolated to determine the state of the entire risk management program," wrote Gerald Talbot, Jr., the administration's associate director for management and administration. "Furthermore, the general recommendations made by the IG were already in place."

Lawrence Livermore has long served as one of the nation's key labs for nuclear research. More recently the lab has focused on monitoring radiation from the ongoing nuclear crisis in Japan and on measures to counter possible chemical and biological terrorist attacks. (AP)