Russia’s bid to prove it is compliant with anti-doping standards has been complicated further after four track and field athletes tested positive for banned drug meldonium. Since the drug was banned by the World Anti-Doping Agency in January, at least 16 sportsmen and women from Russia, including tennis star Maria Sharapova, have tested positive for the substance. The country's athletes were suspended from international competition last year after revelations of widespread cheating and corruption. Russia, which has long shown sporting prowess, could face the humiliating blow of missing out on the Olympic Games, which take place in Rio in August, if it can’t get the suspension lifted.

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