Silva tested positive for drostanolone in an out-of-competition test on January 9, but returned a clean test on January 19. However, he has once again been found to have had drostanolone metabolites in his system in pre- and post-fight tests conducted on the night of his January 31 bout with Nick Diaz.
The Brazilian also tested positive for Oxazepam and Temazepam on the night of the fight, drugs which are used to treat anxiety and insomnia.
NSAC executive director Bob Bennett was damning in his assessment of the latest results.
"I can't speak for the [NSAC] Chairman nor can I speak for the commissioners," Bennett told ESPN.com. "But something I find particularly concerning is that he tested positive on Jan. 9th and then he tested negative on Jan. 19th. If he took this orally, it only stays in your system 5-to-7 days.
"So, obviously, he used it sometime around Jan. 9th and then he used it shortly before the night of the fight. Whether the commission finds this egregious – that he tested positive twice out of three times – is up to them. I certainly find it concerning and unacceptable. It gives an unfair advantage to the person on that. God forbid, a serious injury were to occur to an opponent when someone is on something."
Silva had never previously failed a test for a banned substance and maintained his innocence after his first positive test, asserting that he had "not taken any performance-enhancing drugs".
The 39-year-old was on Tuesday handed a temporary suspension by the NAC pending a hearing.