US nuclear secrets 'missing'

Fires forced the closure of the laboratory last month

A top-level investigation is under way after nuclear weapons data held on computer in a vault at the Los Alamos National Laboratory disappeared.

The data was stored on hard drives which have not been found since a forest fire swept the area and forced workers to leave the site.

When a check was made after the fire, they were not there.

Officials reported the data missing on 1 June - the containers were still in the vault but the hard drives were gone.

"This is an extremely serious matter and we are taking swift actions to deal with it," said John Browne, Director of the Federal Weapons Research Laboratory in New Mexico.

Highly sensitive material

The material involved, according to officials, gave details on how to respond to nuclear accidents and nuclear-related threats from terrorists.

There was also missing material on intelligence on the Russian nuclear weapons programme.

The laboratory has been embroiled in a spying controversy involving a former employee for much of last year.

Wen Ho Lee's daughter protests his innocence

The scientist, Wen Ho Lee, was arrested and charged in December for misuse of secret nuclear data - he is still awaiting trial.

Investigators are accusing him of downloading and copying vast amounts of secret nuclear weapons data from a secure computer at Los Alamos.

Although under investigation for three years in connection with the alleged loss of US nuclear secrets to China, he has not been charged with spying.

But the head of the Energy Department's counterintelligence office is maintaining that there is no evidence of espionage in at this stage in the case of the missing hard drives.

Instead, there is a theory that in the chaos of the forest fire and its aftermath, the drives have simply been mislaid.