Swimmer Ye Shiwen (pictured) won the 200 and 400 metres individual medley at London and was the centre of controversy due to her dramatic improvements.

But Chinese officials always insisted that Ye had done nothing wrong and had been drugs tested properly before the Games.

China's previous sporting successes have been tarnished by athletes testing positive for banned drugs. 

But officials there have now announced that Chinese athletes underwent a total of 272 drugs tests during London 2012 and all were negative. 

China finished second overall at London behind the United States with a total of 88 medals, including 38 gold, their best ever performance in an overseas Olympics.

"We have achieved our goals of the London Olympics, which required both sport and moral excellence," said Liu.Peng, director of China's General Administration of Sports, in his annual report. 

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