In what is likely to be another case of doping ahead of the Rio Olympics, 200m sprinter Dharambir Singh on Tuesday did not travel as scheduled to Rio de Janeiro to take part in the mega event.Highly placed sources told TOI that Dharambir, 27, the first Indian male sprinter to qualify for the Olympics in 36 years, had failed a drug test conducted by the National Anti-Doping Agency and had been told to stay back.It is learnt that the sprinter was scheduled to board the flight to Rio early Tuesday morning but didn’t turn up. When TOI called up Dharambir in the evening, he hung up after confirming his identity.Dharambir could be the third Rio-bound athlete to test positive for a banned drug after shot-putter Inderjeet Singh+ and wrestler Narsingh Yadav. Narsingh+was later cleared to take part in the Games.Officials of the Athletics Federation of India could not be reached for comment despite repeated attempts.Dharambir qualified for Rio at the Indian Grand Prix in Bengaluru in July. Sources said he was told about the failed test three days back. His timings in practice were erratic, raising suspicion.