UFC middleweight Anderson Silva tested positive for the anabolic steroid Drostanolone during an out of competition drug test on January 9th, according to a release from the organization.

The entire release reads:

"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."

Silva made a triumphant return to the Octagon on Saturday at UFC 183, scoring a decisive unanimous decision victory over Nick Diaz in their five round headlining bout.

The 39-year-old had been out of action for 13 months after breaking his leg in a title fight rematch against Chris Weidman.

Silva's opponent Diaz has also tested positive for marijuana in a post-fight 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," the UFC said in a release.

"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."