BERLIN -- South Africa's track and field federation has been asked to conduct a gender test on an 800-meter runner amid concerns she does not meet the requirements to compete as a woman.

Caster Semenya, 18, won the 800 meters at the world championships with a stunningly dominating run.

Semenya took the lead halfway through the race Wednesday and won in a world-leading 1 minute, 55.45 seconds, beating defending champion Janeth Jepkosgei of Kenya by a massive 2.45 seconds. Jennifer Meadows of Britain took bronze.

The world track and field federation requested the gender test about three weeks ago, after Semenya burst onto the scene by improving her personal bests in the 800 and 1,500 by huge margins.

South Africa's Caster Semenya caught the IAAF's attention by greatly improving her personal bests in the 800 and 1,500. Thomas Lohnes/AFP/Getty Images

IAAF spokesman Nick Davies said the "extremely complex, difficult" test has been started but that the results were not expected for weeks.

Semenya qualified for Wednesday's final with a top time of 1 minute, 58.64 seconds. She posted the world's best time this year of 1:56.72 three weeks ago at the African junior championships in Bambous, Mauritius.

Davies stressed that "it's a medical issue, not an issue of cheating."

The verification requires a physical medical evaluation, and includes reports from a gynecologist, endocrinologist, psychologist, an internal medicine specialist and an expert on gender.

"So we're talking about reports that are very long, very time consuming," Davies said.

South Africa team manager Phiwe Mlangeni-Tsholetsane would not confirm that Semenya was having a gender test, but said "there was no cheating on our part."

"We entered Caster as a woman and we want to keep it that way," Mlangeni-Tsholetsane said. "Our conscience is clear in terms of Caster. We have no reservations at all about that."

It was not clear what would happen if Semenya were to medal in Wednesday's final and the test results determined she does not meet the requirements to compete.

"I can't say that if 'X' happens in the future that we will, for example, retroactively strip results. It's legally very complex," Davies said.

"If there's a problem and it turns out that there's been a fraud ... that someone has changed sex, then obviously it would be much easier to strip results," Davies added. "However, if it's a natural thing and the athlete has always thought she's a woman or been a woman, it's not exactly cheating."

He said a decision in such instances is "done on a case by case basis."

"It's something that would have to be considered by the legal experts at that time," Davies said.

Although medals will be awarded for the 800, the race remains under a cloud until the investigation is closed, and Semenya could be stripped of the gold depending on the test results, IAAF general secretary Pierre Weiss said.

"But today there is no proof and the benefit of doubt must always be in favor of the athlete," Weiss said.

Semenya's father, Jacob Semenya, pleaded: "I wish they would leave my daughter alone."

"She is my little girl. I raised her and I have never doubted her gender. She is a woman and I can repeat that a million times," Semenya told the Sowetan newspaper.

Semenya's paternal grandmother, Maputhi Sekgala, also spoke in defense of Semenya.

"The controversy doesn't bother me that much because I know she's a woman -- I raised her myself," Sekgala told The Times, another South African newspaper.

"What can I do when they call her a man, when she's really not a man? It is God who made her look that way," Sekgala said.

Gideon Sam, the president of the SASCOC -- South Africa's Olympic governing body -- congratulated Semenya on a "truly remarkable achievement," the South African Press Association reported.

"We condemn the way she was linked with such media speculation and allegation, especially on a day she ran in the final of her first major world event. It's the biggest day of her life," Sam said.

Morris Gilbert, a media consultant for TuksSport, the University of Pretoria's sports department, said the issue of Semenya's gender has not been raised since the 18-year-old freshman began attending the university.

"It's the first time in South African sport that we have had a gender issue," he said.

He said the university would not get involved in the recent controversy over her gender.

"We are all very proud of her and of what she's achieved," he said. "The university stands behind her all the way."

He attributed her recent success to hard work and rigorous training.

"She trains a lot," he said. "If you go to the athletics track, you're sure to find her there. I don't think she had really good training before she came to the university. She's from a very poor area."

He added: "We had a look this morning, of all the fastest times in the world, she's only ranked 21. So there are a lot of women who run faster."

Semenya is majoring in sports science, he said.

Semenya's rivals said they tried not to dwell on the issue before the race.

"I've heard a lot of speculation, but all I could do was just keep a level head and go about my business," Meadows said. "If none of it's true, I feel very sorry for her."

One thing not in doubt was Semenya's outstanding run.

"Nobody else in the world can do that sort of time at the moment," Meadows said. "She obviously took the race by storm."

Information from The Associated Press was used in this report.