Indian runner Tintu Luka failed to qualify for the 800m final after she finished sixth in the second semi-final in the women's event at the 2012 London Games here Thursday.
Tintu, who is coached by legendary Indian athlete P.T.Usha, clocked 1:59.69 seconds. It was way below her personal best of 1:59.17 secs she achieved two years back.
South African Caster Semenya, who is making her Olympic debut, won the race in 1:57.67 secs.
Semenya, who was sidelined for a year after failing a gender test, is the favourite to win the gold medal.
Semenya won the world title in 2009 at the age 18. After that she was tested and was cleared to return to action in 2010. She finished runner-up in the 2011 World Championships.
Semenya also carried South Africa's flag at the opening ceremony in London.