South Africa's track star Pistorius, commonly known as the "Blade Runner", was arrested on Thursday after his girlfriend was shot dead at his home in Pretoria.
Media have reported the dead woman is believed to be former FHM model, Reeva Steenkamp, who has been dating Pistorius since last year.
Police declined to name 26-year-old Pistorius as the suspect but confirmed that a woman had been found dead at the scene in the upmarket Silver Woods gated community east of the capital.
"We found a nine millimetre pistol at the scene. A 26-year-old man was taken into custody," police spokesperson Katlego Mogale said. She declined to give any further details.
Talk Radio 702 said Pistorius was understood to have shot his girlfriend in the head and arm, although the circumstances surrounding the incident were unclear. He may have mistaken her for a burglar, the radio report said.
Pistorius, who races wearing carbon fibre prosthetic blades after he was born without a fibula in both legs, was the first double amputee to run in the Olympics and reached the 400 metre semifinals in London 2012.
However, things did not go smoothly in the Paralympics with Pistorius suffering his first loss over 200 metres in nine years. After the race, he sullied his media darling pesona by questioning the legitimacy of Brazilian winner Alan Oliveira's prosthetic blades.
The comments sparked controversy though Pistorius was quick to express his regret, going on to describe 100 metres champion Jonnie Peacock of Britain as a "great Paralympic sprinter".
South Africa has some of the world's highest rates of violent crime and some home-owners carry weapons to defend themselves against intruders.
Pistorius' mobile phone went straight to voicemail on Thursday. There was also no response from his agent.
According to South African Sports Confederation and Olympic Committee's (Sascoc) statement on its website: "The leadership at Sascoc has been inundated with enquiries regarding an alleged shooting incident involving team South Africa Olympian and paralympian Oscar Pistorius and his girlfriend.
"Sascoc, like the rest of the public, knows no more than what is in the public domain, which is that there has been an alleged fatal shooting on the basis of a mistaken identity and an apparent assumption of a burglary. The organisation is in no position to comment on the incident other than to say our deepest sympathy and condolences have been expressed to the families of all concerned." – Reuters