Upon further research from other sources,
I find
Wikipedia sites Taiwan as a potential country to blame. The Mori DocID: 1108246 explains
that other countries were reviewed and discounted for various reasons.
Taiwan was amongst them (as was Pakistan) but ‘probably lacked sufficient fissile material for even a single nuclear explosive device.’
To highlight the document’s findings that other countries were discounted, the following quotes are of interest:
‘…West Germany, have possessed both the materials and the technical expertise, none of them…has had the incentive…’
‘Other states that might have nuclear ambitions – such as Brazil, Argentina, and Iraq – almost certainly lacked the fissile material and
nonfissile components required to fabricate and test nuclear explosive devices.
Neither France nor China has agreed to refrain from testing in the atmosphere, but they have recently had no known technical or political motivation
to test clandestinely …
The Soviet Union would have had to assume inordinate political risks in its relations with the United States to have conducted a covert nuclear
explosion in violation of the Limited Test Ban Treaty …for any purpose.’
I find it very interesting that even without the ‘official top-secret’ document being released in years past, that the media from various sources
basically came up with the same idea as the conclusion of the document…that South Africa was the prime suspect, with Israel seen in partnership with
South Africa. The website
nuclearweaponsarchive.org
Is very interesting to read about this topic as the following quote from them highlights:
Unfortunately efforts to detect the one completely unambiguous "smoking gun" signature of a nuclear explosion, guaranteed to silence skeptics,
namely radioactive fallout, failed. The U.S. government quickly launched a major effort to collect samples of the fallout cloud, but Air Force
attempts to sample the fallout failed to enter the low-pressure air mass that had been over the detonation site at the time of the explosion (what the
problem was I do not know). However Dr. Van Middlesworth detected low levels of iodine-131, a short-lived radioactive fission product, in sheep
thyroids in the states of Victoria and Tasmania in western Australia soon after the event. Studies of wind patterns confirmed that fall-out from an
explosion in the southern Inidian Ocean could have been carried there [Barnaby 1989; pg. 17].
Perhaps the white out boxes in Mori DocID:1108246 held more information relating to Israel’s involvement. It looks as though the US could
have gathered conclusive evidence but it may not have been in their interest. …. 
