A report by the Wall Street Journal's John Emshwiller unveiled new evidence which suggests Israel stole bomb-grade uranium from a Pennsylvania nuclear facility in the 1960s to use in its atomic-weapons programme.
The theft, according to the report, occurred at the Apollo nuclear facility in Pennsylvania, owned by Numec, in the mid-1960s. Some 91 kilogrammes of bomb-grade uranium reportedly disappeared. The missing uranium was enough to produce several Hiroshima-sized bombs, the WSJ said.
According to Emshwiller, US officials preferred not to publicise the documents for fear of the potential negative impacts on the US's Middle East peace efforts at the time.
"The question of whether one of America's closest allies was involved in the theft of some of its most valuable and dangerous material in pursuit of nuclear weapons has been one of the enduring mysteries of the atomic age," the report says.
In a memo dated July 28, 1977, a National Security Council staffer under President Jimmy Carter said: "I do not think that the president has plausible deniability" regarding the alleged theft.
However, Zbigniew Brzezinski, Carter's national security adviser, said in a recent interview, even if a theft was proved, "What are we going to say to the Israelis, 'Give it back?'"
A number of FBI officials suspected that Numec's founder and president, Zalman Shapiro, had a role in the theft due to his dealings with Israeli intelligence officials. Shapiro, however, denies the accusations, insisting that his commercial activities with Israel were "legitimate" and "never involved intelligence officials".