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The organisation has blamed the "sheer volume of tickets" sold for the delay, with more than 2 million sold.
Tonight Lotto Powerball jackpotted to the massive must-win amount; reaching the figure for just the second time in its history.
The numbers are: 8, 23, 27, 21, 12 and 22. The Bonus ball is 16, and the Powerball is 1.
But Lotto players are facing a nervous wait, with the official results yet to be released. Normally the result and number of winners are confirmed by 8.40pm.
Marie Winfield, head of communications and corporate social responsibility at Lotto NZ said the high number of ticket sales - which topped 2 million - was behind the delay.
"We're working hard to release the much-anticipated results of tonight's $50 million Must be Won draw, however it's taking us longer than usual," Winfield said.
"This is because of the sheer volume of tickets purchased for the draw, and the fact that we sold more online tickets than ever before.
"We don't have an expected time for the release of the results at this stage.
"We know a lot of people are really excited about the prospect of winning, so sincerely apologise for the delay."
Lotto earlier confirmed that more than 2 million tickets were sold for tonight's draw. At the peak of sales tonight, more than 2000 tickets were being purchased a minute.
More than 1.9 million tickets were sold for the previous $50m must-be-won Powerball jackpot in February, which was won by two players.
Your chances of winning Powerball - one in 38 million - are less likely than you being struck by lightning - one in 280,000 - on your way to buy the ticket.
The odds of winning a must-be-won draw are no different than normal, but the average amount you might win has gone up.
"The odds of winning Powerball haven't changed but the amount you will win 'on average' has gone up," University of Otago statistician Dr Matthew Parry said in February.
"This is because the prize pool has gone up, but also if Powerball isn't struck, there will be more money for prizes in the lower divisions."
Potential winners from tonight will be presented with a book offering support and advice – including of who to tell of their win, and options for investing.