B-sample clears All Black of doping
Tuipulotu's provisional suspension was immediately lifted after the second sample was examined at a World Anti-Doping Agency-accredited laboratory in the United States.
"This is an important and welcomed conclusion for both Patrick and for rugby," NZR Chief Steve Tew said.
"We are pleased that a robust process has been undertaken and that he has been fully cleared."
Tuipulotu returned to New Zealand before the All Blacks' Test against France on their Northern Hemisphere tour last November, for what was then described as "personal reasons".
But it emerged this week that the 24-year-old had been provisionally suspended after a doping test revealed a "specified substance" on WADA's banned list.
New Zealand Rugby Players' Association Chief Rob Nichol said it was unclear why there was a discrepancy between Tuipulotu's A and B samples.
"This is a matter that SMRTL [the US laboratory] is investigating and we look forward to their feedback," he said.
Tuipulotu, who has played 12 Tests and is signed with NZR until the end of the 2019 season, said the episode had been "incredibly stressful" but he was glad the truth had come out.
"I'm pleased the matter is now closed, with my reputation and integrity intact, and I look forward to getting back into training and an exciting year of rugby," he said.
Agence France-Presse
