US nuclear lab loses secret data

Officials are not saying what data has disappeared from the Los Alamos National Laboratory in New Mexico, but it is thought to be highly sensitive.

The laboratory was temporarily closed four years ago as forest fires got dangerously close to it.

Several security breaches have hit the birthplace of the first atomic bomb.

Its closure comes on the anniversary of the first atomic bomb test in Alamogordo, New Mexico.

Its head, John Browne, resigned in January last year, following allegations of theft and fraud, including allegedly questionable purchases and the disappearance of computers and other equipment from the complex.

A few months later, the US National Nuclear Security Administration (NNSA) was instructed by the government to make "aggressive and far-reaching" changes to tighten security at all nuclear weapons laboratories in the US.