Allegations of a plot in which Mr Mandela's ex-wife, Winnie Madikizela- Mandela, and former guerrillas from the ANC's old military wing were implicated were presented to President Mandela in February.
The military intelligence report was endorsed by General Georg Meiring, head of the South African National Defence Force and they implicated General Siphiwe Nyanda, the force's highest ranking black officer, who is expected to replace General Meiring when he retires later this year. There is speculation that General Meiring will be asked to resign.
A spokesman for Mr Mandela refused to give details about the report. At the weekend, President Mandela said he always considered the report a "diversion" and possibly a hoax by the apartheid-era old guard.
It appears the President was forced to act on the report after it was leaked to newspapers following the bizarre arrest in early March in Mozambique of Robert McBride, a foreign affairs official, on gun-smuggling charges. Although a plot to overthrow the government seemed the most outlandish of a host of theories to explain Mr McBride's alleged gun-running, it persisted in the press.
Last Friday, President Mandela announced an inquiry, chaired by Chief Justice Ismail Mohammed and Judge Richard Goldstone, a member of the Constitutional Court and UN prosecutor in the Bosnian and Rwandan war crimes tribunals. It was to concentrate on how the report came to be compiled.
Conspiracy theorists are having a field day but the government believes the "fraudulent" coup only exposes the tensions within the South African armed forces, which are attempting to blend former guerrillas with the apartheid-era government forces. Despite a promising start, integration is going badly.
Where the inquiry's conclusions leaves Mr McBride is unclear. Mr McBride was among those conspirators named in the coup report. Yet this was on Mr Mandela's desk at least three weeks before McBride's arrest.
The government believes that whatever Mr McBride was doing in Mozambique his arrest provided a peg upon which to hang the coup conspiracy. That leaves the possibility that Mr McBride was set up. In another twist it is reported that Vusi Mbatha, with whom Mr McBride was arrested, was the single source for the coup allegations.