Swimming's governing body has suspended London 2012 bronze medallist Yuliya Efimova for a doping offence.
Fina says the Russian tested positive for the steroid DHEA on 31 October in Los Angeles, where she trains at the University of Southern California.
The former world 50m breaststroke record holder won World titles in the 50m and 200m in Barcelona last August.
If a doping offense is proven, Efimova, 21, is likely to keep her medals because the positive test came later.
Her suspension remains in effect until the Fina doping panel meets to rule on the case.
Efimova, who won Olympic bronze in the 200m breaststroke, denied Plymouth-based Lithuanian Ruta Meilutyte a gold medal in the 50m final in Barcelona when she beat her by 0.07 seconds.