Despite failing a doping test for meldonium, world swimming champion Yulia Efimova said Monday she still hopes to compete at the Olympics in August.

In an emotional recorded statement on Russian state TV, Efimova said she tested positive for the recently banned endurance-boosting drug last month and insisted she was innocent.

"I categorically reject the accusation of doping," she said. "At the current time, we are preparing for a hearing into my case. We intend to have the charge completely dismissed and to prove that I didn't break anti-doping rules, and I continue to train with the hope that I will compete at the Olympic Games in Rio."

A four-time gold medallist at the world championships, the breaststroke specialist is widely considered to be Russia's top medal hope in swimming at the Olympics in Rio de Janeiro.

Efimova, who won bronze in the 200-meter breaststroke at the 2012 London Olympics, could be banned for life if found guilty of a second career doping offence.

She was stripped of five European championship medals after testing positive for the banned steroid DHEA in 2013. Efimova's ban on that occasion was reduced from two years to 16 months after she argued that she had taken the substance by accident while trying to buy a legal supplement.

"I missed one and a half years due to my own stupidity," Efimova said. "Since then I track especially carefully anything that enters my body and I give a guarantee that any medicines that I have taken or am taking are allowed."

Efimova said she had taken meldonium for unspecified medical reasons, but stopped before Jan. 1, when the substance became banned in sports. Several other athletes who have failed tests have said they only took meldonium before the ban, announced in September, came into force.

"Although the half-life of meldonium in organism is only 4-6 hours, its complete elimination time from organism is significantly longer," the drug's Latvian manufacturer, Grindeks, said in an emailed statement. "Its terminal elimination from the body may last for several months and it depends on a variety of factors."

Efimova's agent agent, Andrei Mitkov, refused to provide any detail about the medical circumstances that she said led her to take meldonium, telling Russian TV he did not want to give away information before a hearing.

Mitkov said Efimova tested positive in two out-of-competition tests last month while training in Los Angeles. One was administered by swimming governing body FINA and the other by the U.S. Anti-Doping Agency, Mitkov said.

Track athletes test positive

Also Monday, Russia's embattled track and field federation said four of its athletes had tested positive for meldonium at last month's national indoor championships.

The cases pile more pressure on Russia, which was suspended from global track and field in November after a World Anti-Doping Agency commission report alleged systematic, state-sponsored doping. Russia could miss out on the Olympics if the ban is not lifted in time.

Two Russian runners, Andrei Minzhulin and Nadezhda Kotlyarova, have admitted to failing doping tests at last month's championships. Minzhulin won the 5,000 metres at the event, while Kotlyarova reached the semifinals in the 400 at last year's world championships.

Minzhulin told Russia's R-Sport agency that he stopped taking meldonium in November but it remained in his system.

The federation did not identify those who had tested positive but said it was "carefully investigating" the cases and that athletes had been warned several times about meldonium after WADA said in September that it would be banned for 2016.

The IAAF did not respond to a request for comment.

Besides the Russians, there are also ongoing meldonium cases in track and field involving former 1,500-meter world champion Abeba Aregawi of Sweden and former European 800-meter indoor champion Nataliya Lupu of Ukraine.

WADA said Friday there have been 102 failed tests for meldonium so far this year, though it is not clear how many are from particular countries or sports. At least 25 athletes are serving provisional suspensions after testing positive, with more than half of the known cases involving Russians.