UFC 155 drug test results are in from the Nevada State Athletic Commission (NSAC), which on Friday confirmed that all 24 fighters tested for illegal/banned substances after competing at the "Dos Santos vs. Velasquez 2" mixed martial arts (MMA) event on Dec. 29, 2012 in Las Vegas have all passed with flying colors.

Each combatant was screened for performance enhancing drugs such as steroids as well as drugs of abuse such as cocaine and marijuana, among others.

Results from these battery of tests all returned negative.

UFC 155 featured a heavyweight championship main event between Junior dos Santos and Cain Velasquez. Velasquez regained the title he lost to the Brazilian in November 2011 with a five-round shellacking of "Cigano" to become just the second two-time heavyweight champion in UFC history.

Constantinos Philippou, Yushin Okami and Derek Brunson also scored crucial victories on the main card, but the highlight of the pay-per-view (PPV) was the the co-main event which saw Jim Miller defeat Joe Lauzon in a three-round bloodbath.

To relive all the Ultimate Fighting Championship (UFC) action from the weekend be sure to check out our complete UFC 155 results story stream right here.