The 19-year-old, who returned to action in July after an 11-month gender investigation, has been struggling with a back injury sustained in training, though her coach, Michael Seme, had dismissed the problem as a minor niggle.
“She had a slight pain in the back, but the issue has been blown slightly out of proportion,” said Seme.
“She’s going to be 100 per cent fit. We are training and will be there.”
But, hours later, Semeâ€™s decision was overruled on the advice of the South African Olympic Committee doctor.
The Olympic Committee chief executive, Tubby Ready, said the scan â€œconfirmed that she most certainly has a back problemâ€.
Semenya would have been the overwhelming favourite to add the Commonwealth Games 800m crown to the world title she won in Berlin last summer.
Her absence f will be another huge blow for the beleaguered organisers, who have bee