John G.Mabanglo / EPA
South Africa's Caster Semenya reacts after the women's 800m heats at the Olympic Stadium in London on August 8, 2012.
The Associated Press reports — Making her Olympic debut three years after being forced to undergo gender tests, Caster Semenya of South Africa finished second in her 800-meter preliminary heat Wednesday.
Semenya was sidelined for nearly a year while track and field's governing body decided whether to allow her to compete after she won the 2009 world title at age 18. She was tested and eventually cleared to return to action in 2010, then was the runner-up at last year's world championships.
Semenya carried South Africa's flag at the opening ceremony in London and is a leading medal contender in the 800.
Click for more from the 2012 summer games in London.