Oscar Pistorius began his T44 100 metres title defence with a smooth heat win on Wednesday in a time of 11.18 seconds to make Thursday's final.

However, but his complaints about rivals allegedly using longer blades will not be investigated further unless evidence is provided, the International Paralympic Committee (IPC) said.

Moments after a shock loss to Brazil's Alan Oliveira on Sunday, his first 200m defeat in nine years, the South African Pistorius used a post-race interview to question the legitimacy of his defeat.

Pistorius suggested that his opponent's prosthetics were too long which had artificially lengthened his stride, giving him an unfair advantage.

His comments sparked controversy and the South African later expressed regret over the timing of his outburst but the sprinter stuck to his complaint that IPC rules allowed athletes to have an artificially long stride length.

The IPC have received a formal letter from the CEO of the South African Paralympic Committee requesting an urgent investigation into claims that athletes were using different size blades for semi-finals and finals.

However, they found no evidence and claimed it was difficult to investigate any further

A statement read: "We met with coaches of the relevant athletes in the Village yesterday - I have to say there was quite a look of shock on the coaches' faces when we put this to them," Spence said on Wednesday.

"We will look at the measurements from the call room today, but we won't continue investigating unless the South Africans come to us with evidence."