The family of South African runner Caster Semenya has rejected claims that she is a man, hours after reports that sex tests showed she had male internal sex organs.

An investigation into the gender of the 18-year-old began after concerns were raised over her masculine appearance following her victory in the athletics world championships 800m last month.

A source said the tests showed that Semenya had internal testes and no ovaries. The source told the AustralianDaily Telegraph: "There certainly is evidence Semenya is a hermaphrodite."

But Semenya's mother, Dorcus, said that the claims were driven by jealousy at her daughter's talent.

"Why must jealousy drive people to say such bad things? They are crazy. It must be jealousy that makes them say she is a man."

Lesiba Rammabi, Semenya's uncle, said: "I believe Caster is normal, inside and out. What does it matter whether she can have babies? Many people cannot have children. Are those women not women also? We are a normal family who looked at a child when she was born, saw that she was a girl and raised her as any other family would do. Are we now being told that we are wrong?"

If the claims are backed up by the official results, the South African may find herself stripped of her gold medal and be banned from racing.

An Otago University geneticist and paediatrician said yesterday that even if the reports proved correct, it did not necessarily mean Semenya was a hermaphrodite. Professor Stephen Robertson, the head of Otago University's clinical genetics research group, said a hermaphrodite is a person with both ovarian and testicular tissues and is extremely rare.

Semenya could have an "inter-sex" condition but not be a hermaphrodite.

The medical term "inter-sex conditions" refers to a range of genetic and hormonal disorders where normal sexual development is incomplete. Conditions included Androgen Insensitivity Syndrome (testosterone fails to dock with cells and trigger all normal responses) and alpha-5-reductase deficiency (testosterone is not converted to an active form).

The tests on the athlete were carried out in Berlin and involved an endocrinologist, a gynaecologist and a psychologist. Leonard Chuene, the president of Athletics South Africa, said the body stood by the teenager and would be advising her to avoid making any statement until the IAAF had formally told her the test results.

Have there been other cases of intersex conditions in sport?

Yes. Semenya was the eighth case of sexuality issues the International Amateur Athletes Federation has handled since 2005. IAAF secretary-general Pierre Weiss said four of those athletes were asked to stop their career but he gave no further details.

Does the condition automatically disqualify them from elite sport?

No. Eight women "failed" the sex verification test at the 1996 Atlanta Olympics because they had a Y-chromosome. All eight were allowed to compete.

What health implications might there be?

If as has been reported regarding Semenya the person has internal testes, there is a cancer risk and they are usually removed. Semenya reportedly has three-times the female average of testosterone. Removing the testes will reduce this. As testosterone influences muscle development this may impact on athletic performance.

What next for Semenya?

The IAAF is to submit the sex test results to a panel of experts. Its executive council will consider her case when it meets in late November. "It is clear that she is a woman but maybe not 100 per cent. We have to see if she has an advantage from her possibly being between two sexes," Weiss said.

- additional reporting INDEPENDENT