Chinese swimmer Ye Shiwen set an Olympic record Tuesday by winning her second gold medal at the London Games, adding the 200-meter individual medley title to a world-record performance in the 400-meter individual medley.

Ye's second victory comes after her unprecedented performance Saturday in the women's 400-meter individual medley that sparked suspicions of doping.

U.S. swimming coach John Leonard called the performance of the 16-year-old Chinese swimming sensation “unbelievable” and suggested that similar victories in the past have been fueled by performance-enhancing drugs.

China's anti-doping chief Jiang Zhixue told the Xinhua news agency that it is unfair to criticize Chinese athletes because of their success, which he said is the result of training and hard work.

Chinese swimmers have in the past been tainted by high-profile doping scandals, most notably in the 1994 and 1998 world championships.

Ye swam the final 50-meter lap Saturday faster than American Ryan Lochte did in the men's race.