The Russian track and field federation says it is investigating after several athletes had apparently withdrawn from a competition to avoid drug testers.
The All-Russia Athletics Federation (ARAF) says it has "established the fact of a mass withdrawal of athletes due to possible doping controls at one of the ARAF Winter Tour events".
Official results from the eight-race meet in Orenburg showed five athletes who were entered for races didn't start. One women's race was left with just three finishers.
It wasn't immediately clear if any others pulled out earlier and weren't recorded on the results.
Russia is currently banned from international track competitions over widespread doping.
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Since the British drug-testing agency started collecting samples in Russia last year, it has reported athletes trying to avoid testing by withdrawing from races, providing fake urine or simply running away.
