US nuclear lab staff put on leave

Los Alamos has suffered other security lapses

The US's leading centre for nuclear weapons research have sent 15 employees on leave amid an investigation into the disappearance of secret information.

Four other employees have also been sent on leave after an intern was seriously injured with a laser.

Peter Nanos, the director of Los Alamos laboratory in New Mexico, said security breaches were threatening the centre.

Classified work at the lab was halted last week while a search was carried out for two missing computer discs.

Mr Nanos said the staff members placed on leave would not be allowed back into the centre unless they were escorted and their visit related to the investigation.

He did not identify what posts the employees had held. "Suffice to say it's all levels," he was quoted by the Associated Press as saying.

'Denial'

Mr Nanos said attitudes towards security at the laboratory needed to change.

"It has become apparent to me... that our biggest challenge at Los Alamos right now is dealing with culture," he told a press conference.

LOS ALAMOS LABORATORY Isolated site chosen by J Robert Oppenheimer, 'father' of atomic bomb Facility built first atomic bomb, nicknamed 'The Gadget' and tested on 16 July 1945 Produced 'Little Boy' and 'Fat Man' atomic bombs dropped on Hiroshima and Nagasaki, Aug 1945 Part of US Dept of Energy and managed by University of California Involved in nuclear weapons development and defence, energy and environmental projects Nuclear fuel cycle

"There are a lot of people at Los Alamos who are in a state of denial."

The two computer discs were reported missing two weeks ago from a unit known as the Weapons Physics Directorate.

Officials ordered a detailed inventory of sensitive data at the lab; and staff with access to the items in question were allowed on to the plant under escort only.

The NNSA, the federal agency which oversees the industry, sent a team to Los Alamos to investigate the disappearance.

Los Alamos - birthplace of the first atomic bomb - has been hit by a series of embarrassing security breaches.

But this is thought to be the first time work at the centre had to be suspended for security reasons.