MOSCOW Russian swimmer Yulia Efimova, who won a bronze medal at the London Olympics, has failed a doping test, the Vedemosti newspaper reported on Friday.
The sample was taken in October, a month after the 21-year-old won two gold medals at the world championships in Barcelona.
Efimova, the short course world record holder in 50 and 200 meters breaststroke, allegedly tested positive for the banned steroid DHEA.
She has admitted taking food supplements and if the results are confirmed could face a two-year ban, the report said.
Russian Minister for Sport Vitaly Mutko said he would wait for an official announcement.
"Such information should only be made public following an announcement by the responsible disciplinary bodies," he told R-Sport news agency.
"In sport there are always problems with ones health and the treatments they take. There may be nuances in every athlete's life."
The head of the Russian anti-doping agency said the organization had not been handed any details about the case.
"We have not received any information about the possible disqualification of Efimova at the moment," Nikita Kamaev told ITAR-TASS news agency.
Efimova is likely to challenge the positive result and would get the chance to have her "B" sample tested. The 21-year-old would be the fourth Russian swimmer to have tested positive for a banned substance since the 2012 London Olympics, after Ekaterina Andreeva, Natalia Lovtsova and Ksenia Moskvina.
(Reporting by Dmitry Rogovitskiy, Editing by Ed Osmond)