The World Anti-Doping Agency says some athletes who tested positive for meldonium may be able to avoid sanctions because of a lack of certainty over how long the drug takes to clear the system.

WADA says provisional suspensions can be lifted if it is determined that an athlete took meldonium before it was placed on the list of banned substances on Jan. 1.

More than 120 positive tests for meldonium have been recorded since the drug was prohibited by WADA. The highest profile case involves Russian tennis star Maria Sharapova, who announced that she tested positive during the Australian Open in January.

In a notice sent to national anti-doping agencies and international sports federations, WADA says ''limited data exists'' on the time it takes for meldonium to clear the system.

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