Graeme McDonnell 
The UFC have confirmed that Anderson Silva failed his UFC 183 pre-fight “out of competition” drug test for Drostanolone metabolites and Androstane. Nick Diaz has also failed a UFC 183 drug test. Nick’s failed test was for marijuana and was found in his post-fight test. News was first reported by Kevin Iole
Anderson Silva failed for “Drostanolone metabolites on his Jan. 9 out of competition drug test” which is an anabolic steroid and for Androstane which is a form of endogenous steroid hormone.
Anderson Silva AND Nick Diaz fail drug tests … Silva's failure was on a PRE-FIGHT test. Diaz post-fight test for marijuana. Story coming
— Kevin Iole (@KevinI) February 4, 2015
Silva popped for drostanolone in a PRE-FIGHT test conducted Jan. 9. Diaz over limit for marijuana from post-fight test
— Kevin Iole (@KevinI) February 4, 2015
NSAC tested Silva out of competition on Jan. 18 also. Those results are not in. NSAC chairman says results of Jan. 9 test came in today.
— Brett Okamoto (@bokamotoESPN) February 4, 2015
The Nevada Athletic Commission (NAC) executive director Bob Bennett confirmed Diaz’s positive test with MMAFighting‘s Ariel Helwani
Also, per Bennett, Silva tested positive for 2 PEDs on 1/9. The other one found in his system was androsterone.
— Ariel Helwani (@arielhelwani) February 4, 2015
The UFC released a statement on the situation with Anderson Silva
“On February 3, 2015, the UFC organization was notified by the Nevada State Athletic Commission that Anderson Silva tested positive for Drostanolone metabolites on his Jan. 9 out of competition drug test. UFC’s understanding is that further testing will be conducted by the Commission to confirm these preliminary results.
“Anderson Silva has been an amazing champion and a true ambassador of the sport of mixed martial arts and the UFC, in Brazil as well as around the world. UFC is disappointed to learn of these initial results.
“The UFC has a strict, consistent policy against the use of any illegal and/or performance enhancing drugs, stimulants or masking agents by its athletes.”
Read here for more on this article and some of the ways athletes may use to avoid positive drug tests.
Anderson Silva released a statement to Ariel Helwani of MMAFighting
“I’ve been competing in this sport for a very long time. This is my nineteenth fight in the UFC. I have been thoroughly tested many times and have never had a positive drug test.
“I have not taken any performance-enhancing drugs. My stance on drugs is, and will always be, the same. I’m an advocate for a clean sport.
“I’m consulting with my advisors right now to explore all of my options and intend to fight this allegation and clear my name. I will not make any further comments until my team advises me to do so.”
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The UFC statement on Nick Diaz’s failed test
“The UFC has been notified by the Nevada State Athletic Commission that Nick Diaz has tested positive for marijuana metabolites following his fight with Anderson Silva at UFC 183 on Jan. 31 in Las Vegas, Nev. The UFC has a strict, consistent policy against the use of any illegal and/or performance enhancing drugs, stimulants or masking agents by our athletes.
As a result of his positive test, Diaz has been informed that he has violated the UFC Fighter Conduct Policy and Promotional Agreement with Zuffa, LLC. The UFC organization will fully respect the Commission’s final decision relating to Diaz at a disciplinary hearing set for February 17.”
Nick Diaz was double the legal limit for marijuana. Test was given to him at 10:38pm PT on Jan 31http://t.co/peMS3Rr3zl #UFC #UFC183
— Damon Martin (@DamonMartin) February 5, 2015
must of been a good session