Anderson Silva and Nick Diaz both fail UFC 183 drugs tests

Silva had won their fight by a unanimous decision

Anderson Silva and Nick Diaz trade blows during their fight at UFC 183 last weekend (GETTY IMAGES)

Anderson Silva, known to many as the greatest UFC fighter of all time, has tested positive for anabolic steroids.

The UFC announced last night that the Brazilian tested positive for the steroid drostanolone during a random out-of-competition drugs test administered by the Nevada State Athletic Commission on 9 January.

It was the first time 'The Spider', who has won 34 out of his 41 MMA fights, had tested positive for a banned substance in his nearly 18-year career.

Silva, 39, returned from 13 months out injured with a broken leg last weekend to defeat Nick Diaz at UFC 183 in Las Vegas. It was also revealed last night that his opponent Diaz had failed a drugs test, testing positive for marijuana metabolites in his post-fight test.

The NSAC said that the results of the pre-fight test were not available until yesterday morning, which is why the fight was not cancelled.

"On Feb. 3, 2015, the UFC organization was notified by the NSAC that Anderson Silva tested positive for drostanolone metabolites on his Jan. 9 out of competition drug test," the UFC said in a statement. "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."

On Diaz, the UFC released this statement: "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."

Full disciplinary hearings will be scheduled for each fighter, where they could face suspension