Deputy US Energy Secretary Kyle McSlarrow and other officials Monday toured the top secret laboratory in New Mexico at the start of a comprehensive review of security problems that shut down all work at the key installation which holds many US nuclear secrets.

The officials "have thus far concluded that the failure to follow appropriate procedures is widespread and extends beyond the security area," Abraham said in a statement.

He said classified operations would not resume until the investigators are satisfied "that the newly implemented corrective actions provide for complete and verifiable custodial control of such media."

The visit came after all secret operations and virtually all other work were idled at the plant where the atomic bomb was born in 1945 after a several security violations that officials have branded as "unacceptable."

The unprecedented step was taken after classified computer storage disks possibly containing nuclear secrets were reported missing July 7 and after classified information was sent out in unclassified e-mails that hackers could have gained access to, officials said.

Theories of how the storage disks disappeared ranged from innocent misplacement of the disks to nuclear technology theft.

Around 7,800 people are employed at the site by the University of California, which runs Los Alamos, while up to 13,000 people can be present at the laboratory during the busy summer months.

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