The remarkable world record, gold medal winning performance of 16-year old Chinese swimmer Ye Shiwen in the final of the women's 400 Individual Medley is being called into question by a top US coach.

John Leonard, the executive director of the World Swimming Coaches Association, called Ye's time in the freestyle leg where she swam as fast as men's winner Ryan Lochte, "impossible." And Leonard has even accused Ye and the Chinese team of using "East-German" style doping tactics to achieve their success.

The 16-year old Chinese swimmer Ye Shiwen wins her second gold metal in London Olympic Games on July 31, 2012. [CNTV]

Ye however, has tested clean passing the comprehensive anti-drug testing at this year's games and on Monday, the IOC's chief anti-doping official said there is no reason to believe Ye is anything but clean.

Ye claimed the world championship in the same event in Shanghai last year, but her swim in London shaved seven seconds off her time, which has certainly raised eyebrows within the swimming world. No Chinese athlete has tested positive for a banned substance thus far in London.