Russia's swimming federation confirmed that it had received documents from the sport's governing body "confirming the temporary suspension of the sportswoman from competition in connection with a possible doping rule violation".
Russian media reported that 23-year-old Efimova – who won a bronze medal at the London Olympics and trains in the United States – faces a life ban after becoming the latest athlete to test positive for meldonium, a substance banned on January 1.
This could be a repeat violation, as she was banned for 16 months after failing a test for a banned steroid in October 2013.
The news of the suspension came as Ukraine's athletics federation on Thursday said 800-metre runner Natalya Lupu would not compete at the 2016 indoor world championships for also using meldonium.
"Wada has some questions related to the use of meldonium for Natalya Lupu," the federation said in a statement.
"In connection with this it was decided to cancel Natalya Lupu's trip to the Portland world championships."
The fallout over meldonium exploded into public view when Russian tennis star Maria Sharapova admitted earlier this montsuspectthat she had tested positive for the substance at the Australian Open in January.
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