The U.S. Air Force nearly detonated an atomic bomb over North Carolina in 1961 that would have been 260 times more powerful than the device that destroyed Hiroshima, according to a declassified report published Friday in The Guardian.

The 1969 document, obtained by investigative journalist Eric Schlosser under the Freedom of Information Act, details the Jan. 23, 1961, B-52 crash near Goldsboro, North Carolina, that saw two Mark 39 hydrogen bombs break up in mid-air.

The report said that one of the two bombs behaved exactly as nuclear weapon is designed to function in wartime and that only a single low-voltage switch prevented detonation. Fallout could have been deposited over Washington, Baltimore, Philadelphia and New York City, according to the report.

Parker Jones, a senior engineer in the Sandia National Laboratories in Albuquerque, N.M., wrote in the report that “one simple, dynamo-technology, low voltage switch stood between the United States and a major catastrophe”.

Jones, analyzing a book by physicist Ralph Lapp on the crash, found that the bombs “did not possess adequate safety for the airborne alert role in the B-52” and concluded that the detonation “would have been bad news – in spades.”

•Credit (except headline): New York Post. Photo shows Hiroshima atomic bomb blast.