The British newspaper "The Guardian" reports that recently declassified documents from the United States show a hydrogen bomb almost exploded in the state of North Carolina in 1961.
The documents, obtained based on a Freedeom of Information Act request, show that two hydrogen bombs fell from a B-52 bomber when the plane broke up in flight.
One of the bombs initiated an explosion sequence.
Parker Jones at the Sandia National Laboratories wrote about the mishap in a classified report in 1969, saying investigators discovered three of the four safety switches to explode the bomb had been triggered.
Jones wrote safety mechanisms to prevent arming the bomb were "not complex enough" and "one simple, low voltage switch stood between the United States and a major catastrophe."
With each bomb carrying a payload of four megatons, the explosion would have been 260 times more powerful than the atomic bomb dropped on Hiroshima at the end of World War II.
Based on reporting by AP and AFP