South African teenager Caster Semenya, whose rapid improvement has prompted officials to order a gender verification test, won the women's 800 metres title with a crushing performance at the World Athletics Championships in Berlin.
Powerfully-built but beautifully relaxed in motion, the 18-year-old clocked 1 minute, 55.45 seconds for the year's fastest time and a personal best by more than a second.
Kenyan defending champion and Olympic silver medallist Janeth Jepkosgei, who was tripped by Semenya and fell in the heats only to be reinstated, was more than 15 metres adrift for second.
Fast-closing Jenny Meadows of Britain snatched third, three-hundredths of a second behind Jepkosgei in another personal best.
International Association of Athletics Federations general secretary Pierre Weiss says an investigation into Semenya's gender was underway in both South Africa and Berlin.
He says the IAAF allowed her to compete because today there is no proof and the benefit of doubt must always be in favour of the athlete.
Weiss said because of Semenya's age, the IAAF had decided to keep her away from a news conference following her victory.
He added doctors consulted by the IAAF said it would take days or even weeks before a conclusion could be reached from her gender test.