"Marmageddon" has spread south following confirmation brewer's yeast sourced from Dunedin's Speight's brewery is now used solely for cattle feed.
For three decades, Lion Nathan breweries in the South Island supplied brewer's yeast to Sanitarium for the production of Marmite.
However, Sanitarium's Christchurch factory closed late last year because of earthquake damage.
The factory is the only one producing the popular spread and, while it expected to be producing the spread again in July, supplies are running out in New Zealand and across the Tasman.
The Christchurch plant produces an estimated 640,000kg of Marmite every year, with yeast accounting for 80% of the ingredients.
A Lion Nathan spokeswoman said the yeast supplied to make marmite was used to make all of the brewery giant's beers apart from wheat beers.
For each batch of beer the brewer uses about eight generations of yeast. With each generation three times the size for each repatching, the yeast not required at each step in the brewing process - and all of the last generation - previously went to Sanitarium.
The spokeswoman confirmed the other market for the brewer's yeast was to a stockfood company, which sold it for cattle feed.
Sanitarium has issued a statement on its website saying, "Don't freak! We will be back soon."
