US nearly exploded nuclear bomb over North Carolina

An atomic bomb 260 times more powerful than the device that devastated Hiroshima was nearly detonated over North Carolina in 1961, a declassified document has revealed.

Only a low-voltage switch stood between millions of deaths from an unprecedented blast that would have reached Washington, Baltimore, Philadelphia and New York.

The US government has confirmed before that two Mark 39 hydrogen bombs were mistakenly dropped over the US state when a B-52 bomber broke up in mid-air on a routine flight.

But the document, published by the Guardian after being obtained by a journalist under the Freedom of Information Act, reveals the threat of disaster was far bigger than previously known with one of the bombs beginning its detonation process in descent.