"Swiss industry got around the arms embargo that the U.N. had imposed on South Africa in grand style," said Peter Hug, a historian who produced one of the reports in the Swiss National Science Foundation's six-year investigation into Swiss-South African relations.
Germany was among the countries that also played a role, Hug said, but he gave no details on their involvement.
"The fissionable material needed for this originated from the uranium enrichment that South Africa had built up with technical support from Switzerland, Germany and other countries," Hug, a history professor at the University of Bern, wrote in his 11-page report for the project.
South Africa built six nuclear weapons and partially assembled a seventh between the 1970s and 1993, when then-President F.W. de Klerk stood in front of Parliament to disclose the program and announce that the bombs had all been dismantled.
De Klerk renounced the program that had been aimed at neighboring states opposed to apartheid and Cold War instability that was fueling the war in nearby Angola.
Hug said a handful of companies and a government research institute were involved in South Africa's atomic program.
The report cost 2 million Swiss francs, about US$1.5 million or Ђ1.3 million, AP reported. V.A.