Olympic swimming medalist Yulia Efimova of Russia faces a possible lifetime ban after being provisionally suspended for a second doping violation. Her U.S.-based coach said Efimova has indicated she wants to fight the accusation.

The 23-year-old breaststroke specialist who has won four world titles and an Olympic bronze medal is the latest high-profile name caught up in the series of doping scandals that have dogged Russia over the past two years. She owns the world's fastest time in the 100-meter breaststroke and the second quickest in the 200 breast this year, and is considered one of Russia's top medal hopes for the Rio Olympics in August.

In a brief statement, the Russian Swimming Federation said it had received documents from international governing body FINA stating that Efimova was suspended "in connection with a possible breach of anti-doping rules."

The federation did not confirm reports in the Russian media that Efimova tested positive for meldonium, the same substance found in tennis star Maria Sharapova's sample at the Australian Open in January.

If Efimova's case is confirmed to be a positive test for meldonium, her earlier medals would not be affected because the substance has only been banned since Jan. 1.

Efimova trains in Los Angeles under Dave Salo, who coaches at the University of Southern California.

"Yulia stopped taking it (meldonium) in December when it became evident it was going to be on the banned list," Salo told The Associated Press by phone Thursday from Atlanta, where he is coaching at the NCAA women's swimming and diving championships. "She sent me a text almost immediately yesterday and tried to assure me that she hadn't done anything since December."

Salo said any athlete training under him is subject to drug testing by WADA and USADA, which visit his pool weekly, unlike some other countries where testing is less stringent.

"It's not coming from me, it never has come from me," Salo said. "I don't think kids need supplementation of any sort. I've never counseled kids to take anything. They know my stance on it."

Salo said his role in Efimova's career involves only training and coaching in the pool, and she has others who oversee her physical therapy, weight training and nutrition.

"I don't know who's counseling her in Russia," he said. "She's a great kid, she's a hard-working person. She's tremendously talented, she doesn't need these things to be successful."

Salo said the larger problem in swimming is athletes seeking an edge who listen to outside influences such as doctors, yoga instructors and other swimmers, as well as some coaches who suggest supplements.

"We've created an environment where there's an expectation that these kids have to take something," he said.

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 offense.

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.

Efimova returned from that ban to win gold in the 100-meter breaststroke at last year's world championships in Kazan, Russia.

Salo said he would speak to Efimova when he returns to Los Angeles next week.

"Her text was, 'Please believe me. I didn't do this on purpose,'" he said. "I believe her. She's culpable to the extent that she has a lot of other people in her ear."

Efimova is in the U.S. as part of a program in which the Russian swimming federation sends top athletes abroad for specialized coaching. Federation coach Sergei Ilin told Russian news agency RIA Novosti that none of the other top Russians based in the United States was under suspicion of doping.

"If we're talking about the group of athletes in the U.S., then so far this case is just about Efimova," he said.