These are the first violations detected since 2009 when the NZRU adopted the New Zealand Sports Anti-Doping Rules - a standard set of rules applicable to a broad range of New Zealand sporting codes.
NZRU general manager of professional rugby Neil Sorensen said rugby's record showed the sport was relatively untainted by drugs.
"Two violations this year are two too many, but there were unusual circumstances in both cases and we don't think they are indicative of any significant problem with drugs being used to enhance performance.
"The cases are certainly a timely reminder to all players that they need to be aware of their obligations as the consequences for their careers can be severe."
DFSNZ chief executive Graeme Steel said it was disappointing the two cases had occurred within a sport which provided excellent co-operation.
"Rugby is a sport in which doping can have a real impact on performance, but these cases did not appear to have any such tendency and we will work hard with the NZRU in an effort to prevent similar breaches occurring in the future."
DFSNZ is responsible for the rugby anti-doping programme, and conducts drug testing on players from provincial level upwards or where evidence of use may exist elsewhere. This year's testing programme did not include Rugby World Cup 2011 where testing was carried out by Rugby World Cup Ltd.
A total of 216 urine and 76 blood samples were tested during the tournament, yielding just one positive test. The player, whose identity and team is yet to be disclosed, tested positive for a banned painkiller following the final round of the pool phase. His team failed to progress to the knockout stage, and the player has since been provisionally suspended by the IRB pending the outcome of a hearing.