Indian Gold Medalist wrestler fails doping drug test
Olympic squad less than two weeks before the Rio Games begin.
Yadav, a Commonwealth Games gold medallist, qualified for next month's Olympics in the 74-kilogram freestyle category, but tested positive for a banned steroid during routine testing.
A subsequent sample known as a B sample was also found to be positive.
"Narsingh was personally present when his B sample was opened," National Anti-Doping Agency director general Navin Agarwal told the Press Trust of India news agency.
"He appeared before a disciplinary panel yesterday (Saturday). The panel sought more reports regarding the matter," Agarwal said.
Agarwal said a decision had not yet been made on removing the 26-year-old from the Rio-bound squad, adding it was "too early to comment".
"We will try to complete the whole thing quickly."
Further hearings would be held into the case, the government said in a statement, confirming the positive test but not naming Yadav.
There was no immediate comment from Yadav, the son of a milk vendor, who won gold at the Commonwealth Games in 2010 but came home-empty handed from the London Olympics two years later.
The news could open the door for champion wrestler Sushil Kumar, India's most successful individual Olympian.
Kumar failed to qualify for Rio despite winning bronze at the 2008 Beijing Games and silver in London, both in the 66-kilogram freestyle category.
Kumar launched a legal battle to win the right to compete against Yadav for the sole spot in the Indian squad for the 74-kilogram category, after his 66-kilogram favourite event was axed.
But Delhi's High Court last month sided with the International Wrestling Federation which ruled that Yadav, a 2015 world championship bronze medalist, had already qualified.
The Olympics start on August 5.