South Africa has been developing nuclear weapons for years and may have begun producing them in 1979 or earlier, says a newly disclosed CIA document.

The memorandum, obtained by the environmentalist Natural Resources Defense Council under the Freedom of Information Act, was written in December 1979 at the request of the National Security Council. It sought to determine who was responsible for a nuclear explosion detected on Sept. 22, 1979, by a U.S. Vela satellite off the African coast.The document did not appear to present a conclusive answer, unless it was hidden in the portions that were blacked out for reasons of national security. While all the intelligence agencies appeared to agree South Africa could have done it, they differed on whether it did.