"I think anyone who bought a ticket at Pak'nSave Riccarton will be checking pretty quickly,'' said Lotto corporate communications manager Emilia Mazur.
"Someone in Christchurch has just won an incredible amount of money.
"We'll give it some time before we start doing our own investigations.
"People who know they've won can take some time to think about things, but with these big wins, they usually collect pretty quickly.''
It is the third biggest prize won with Big Wednesday, which requires selecting the correct six numbers and the right coin toss.
The largest Big Wednesday prize of $36.9m was won by a Masterton family syndicate in 2009, and the second largest prize of $27m was won by a young man in Tauranga in September last year.
This big prize payout begins a week of winning, with Lotto New Zealand ready to give away more than $54m to lucky players - the biggest prize week in the game's history.
Powerball's Must Be Won draw on Saturday will see at least $32m won by one or more lucky Lotto Powerball players.
The Powerball jackpot has increased with sales during the week so far, and the current First Division prize pool now stands at $32m.
