The world swimming champion Yulia Efimova of Russia failed a doping test for meldonium but said she still hoped to compete at the Rio de Janeiro Olympics in August.
Efimova, a breaststroke specialist and a four-time gold medalist at the world championships, is widely considered Russia’s top medal hope in swimming at the Olympics.
Also, Russia’s embattled track and field federation said four of its athletes had tested positive for meldonium at last month’s national indoor championships. Vitaly Mutko, the sports minister, was quoted as saying that the string of doping scandals had worn him down, an apparent suggestion that he might leave his post.