Colonel Matheson, of the South African Railways Police, testified on investigations into the background of every passenger, crew member, and other person associated with the aircraft. Colonel Matheson negatived sabotage as a possible cause.
....... so that means it wasn't! There were many cover-ups in those days, as there are now, just that the Nats were better at it.
Anyway, not my conspiracy theory at all, it was what went round in those days.
The mystery of the Rietbok (Non Fiction)
The Rietbok crash, however, had some sinister connotations which to this day are still unsolved, also there are hints and allegations of government conspiracies and cover ups with new evidence coming to the fore every now and then.