BERLIN — Facing questions about her gender, South African teenager Caster Semenya easily won the 800-meter gold medal yesterday at the world championships.

Her dominating run came on the same day track and field's ruling body said she was undergoing a gender test because of concerns she does not meet requirements to compete as a woman.

Semenya took the lead at the halfway mark and opened a commanding lead in the last 400 meters to win by 2.45 seconds over defending champion Janeth Jepkosgei in a world-leading 1 minute, 55.45 seconds.

Semenya had burst onto the scene by posting a world-leading time of 1:56.72 at the African junior championships in Maruitius.

Her dramatic improvement in times, muscular build and deep voice sparked speculation about her gender. Before the race, IAAF spokesman Nick Davies stressed this is a "medical issue, not an issue of cheating."

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