Facebook followers widely urged the winners to keep the secret to themselves, with little conjecture or hints as to who may have won.
"They live in Flaxmere," said one message, though there was no clarity as to whether that was fact, rumour or local gossip. Another read: "Shame on you for asking."
While the holder of the Hastings ticket had not come forward, there had been a claim from co-winners who bought a ticket at a superette at Kumeu, West Auckland.
A Lotto spokesman said Auckland grandparents had won half the other half of the pool, which comprised a Powerball first-division jackpot of $25,933,214 and two quarter-shares of the Lotto first division prize of $1million.
The two were unaware they held the winning ticket until the day after the Saturday-night draw, when they checked online and found they had a matching line with the six Lotto numbers and the Powerball supplement.
A woman told Lotto staff her husband "thought I was having him on", so they went to a Lotto shop for confirmation.
"That's when I went weak at the knees," she said. They planned to buy their own house, a holiday house for the children and grandchildren to enjoy spending time at together, and a boat to please the grandfather.