Questions have been raised about the gender of a South African athlete who won the 800 metres women's event at the world championships in Berlin.
The International Association of Athletics Federations says it demanded a gender test three weeks ago amid fears that Caster Semenya, 18, should not be able to run as a woman, the BBC reports.
Semenya won gold in impressive fashion on Wednesday, leaving her rivals trailing as she won in a time of 1 minute, 55.45 seconds.
Defending champion Janeth Jepkosgei was second, 2.45 seconds adrift, with Britain's Jennifer Meadows taking bronze.
IAAF spokesman Nick Davies said the "extremely complex, difficult" test results were not due for several weeks.
The South African athletics federation insists it is "completely sure" that Semenya is a female.
The question of her gender was raised thanks to her masculine appearence, performance in the race, and deep voice.