South Africa's newly-crowned women's 800 meters world champion Caster Semenya must undergo a gender test, the sport's governing body the IAAF announced on Wednesday.
The 18-year-old has been a revelation this year first domestically, where she vastly improved her times at 800m and 1,500m, and also here where she romped to the title trouncing defending champion Janeth Jepkosgei by over two-and-a-half seconds.
Semenya did not attend a post-race press conference; IAAF secretary general Pierre Weiss took her place.
"I am replacing the winner here tonight. A double investigation is being conducted - one in South Africa, one in Berlin," said Weiss.
He reiterated that the outcome of the gender test would not be known for some time.
"I am not a doctor, but all the doctors who conducted investigations tell me this sort of thing takes weeks or months," said Weiss.
Weiss insisted that it was not fair to put such a young and inexperienced athlete up in front of the press.
"We know you want to talk to her, but she is young, she is inexperienced and she is not able to reply properly to all your questions.
"I will answer for her. The decision not to put her up her was taken by the IAAF and the South African federation.
"I repeat, she was not prepared for a situation like this.
"If at the end of the investigation we find out she is not a woman, we will withdraw the medal and redistribute it. But there is nothing which would have stopped her from running today."
Weiss said that they would be completely open once the investigation was finished.
"The investigation is confidential, but we play the game of transparency and when we announce our investigation, I hope the doctors will explain fully. In truth, I have no idea what the investigation involves."
Weiss admitted it was a headache that the IAAF could have done without, but as Semenya had been a total unknown a few weeks ago it had not been a problem they had anticipated.
"We would have preferred no controversy.
"She was unknown three weeks ago, nobody could have anticipated this situation, we are fast, but we are not that fast."
Earlier IAAF spokesman Nick Davies revealed the question had first been raised after Semenya's astonishing performances at the African junior championships.
"In the case of this athlete, following her breakthrough in the African junior championships, the rumours, the gossip were starting to build up," said Davies.
Semenya has already been involved in a controversial incident at the championships.
During the 800m heats, she became entangled with Janeth Jepkosgei on the final bend and brought down the Kenyan.
Semenya managed to just about keep on her feet, showed great composure and ran out an easy winner.
She has also displayed a certain nonchalance regarding her future in the sport as was in evidence after her semi-final on Monday.
"Running is just a game for me," said Semenya. "Even next year, I can stop running if I want."
There have been precedents in such cases, the most famous being that of Polish athletics great Stella Walsh (also known as Stanislawa Walasiewicz) who won Olympic gold in the 100 yards at the 1932 Olympics and silver in the same event in the 1936 Olympics here in Berlin.
However, after she was shot dead during an armed robbery in 1980, the subsequent autopsy revealed she possessed male genitalia, although she also had female characteristics as well.
The International Olympic Committee (IOC) have now dropped gender determination tests.