US: Secret work on US nuclear weapons at one of America's top laboratories has been halted and a government inquiry launched after two computer disks went missing, the third such security breach in eight months.
The disappearance of the disks from the Los Alamos base in New Mexico was blamed on sloppiness among laboratory scientists, whom their manager described as "cowboys" for their disregard of security rules, rather than on espionage.
The scandal has jeopardised the University of California's contract to manage Los Alamos, where nuclear weapons are designed and maintained, and which the university has run for more than half a century.
Last year, the energy secretary, Mr Spencer Abraham, warned that it would have to compete for its contract for the first time, after a string of incidents.
In 1999 a Los Alamos scientist, Wen Ho Lee, was wrongly accused of spying for China after taking classified material out of the laboratory.
In 2000 two computer hard-disk drives containing an encyclopaedia of all the world's known weapons designs went missing and were later found behind a photocopier. Last year two vials of plutonium went missing.
In the latest incident, two disks and two disk drives were mislaid, but the drives were found hours later, when it was discovered a laboratory employee had taken them to another building.
The two disks, containing highly sensitive data from the weapons physics directorate, are still missing.
