All Blacks lock Patrick Tuipulotu is said to be shocked by a positive drugs test result which has seen him suspended.
New Zealand Rugby and the New Zealand Rugby Players Association has confirmed that they were notified of a positive test result in November.
The statement has declared that:
"NZR and NZRPA can confirm that Patrick was shocked by the test result and is working hard to identify the source of the Specified Substance.
"In accordance with World Rugby Anti-Doping Regulations, Patrick remains provisionally suspended pending resolution of this matter.
"Further to these regulations, NZR and NZPRA are bound by strict confidentiality obligations."
The rugby star and Blues player has not been seen on the pitch since November, after returning home early from a Northern Hemisphere tour, amid what has been described as an "ongoing personal matter".
The results were discovered in the lead-up to the final test of the season against France. It is also understood that circumstances surrounding the case are of a sensitive nature.
A spokesperson for the Blues told the Herald it would not be making any comment or statement on the allegations.
Tuipulotu toured the Northern Hemisphere with the national side last November, starting against Ireland in Chicago and then against Italy in Rome but the giant second rower returned home a week early, along with injured flanker Sam Cane and utility back Ben Smith, for what coach Steve Hansen described at the time as "personal reasons".
Last week, it was confirmed Tuipoluto would not report for duty with the Blues Super Rugby franchise this week and would be sidelined indefinitely by an "ongoing personal matter".
New Zealand Rugby Players' Association rep Rob Nichol confirmed to the Herald last week Tuipulotu would not start pre-season training, but he would not elaborate any further on the issue. His management also refused to comment.
In December, the 23-year-old lock was named a family chief in Samoa. He was bestowed the chiefly title of Sa'u, from the village of Apolima.
The young All Black grew up in New Zealand and attended Auckland's St Peter's College. He told the local Samoa Observer that becoming a matai - chief - was an honour and acknowledged the responsibilities that would come with it.