Two people have died and three others have become ill in a listeria outbreak believed to have originated in hospital food in two different regions.
The affected products have also been recalled from shops as they may contain the bacteria causing the disease.
The two elderly women died after contracting listeria, a food-transmitted illness found in meat supplied to the Hawkes Bay Hospital.
Two other people contracted the disease but recovered.
Hawkes Bay Hospital spokesman Andrew Coleman says another case has been reported today at Tauranga Hospital.
"At this stage there doesn't seem to be any any correlation between what's happening in Hawkes Bay with these cases, relating to the death and illness.''
The cause of the women's deaths in Hawkes Bay - in June and this month - were reported a day after the recall notices were placed in newspapers by Napier company Bay Cuisine.
The company supplies the hospital's kitchen and cafeteria, and the Mad Butcher and Preston shop chains.
The products included Mad Butcher 500g salami and pepperoni rolls.
The products, as well as Ratanui Hams and EZY Carve boneless leg ham, are sold in Mad Butcher and Preston stores in Wellington, Porirua and Palmerston North.
The recall notice warned that the products "must not be consumed".
Four patients with listeria went to the Hastings hospital between May and June but the Hawkes Bay District Health Board said it was still unclear if they had contracted the illness while in its care.
However, it could not completely rule out the possibility.
Health board chief executive Kevin Snee said: "It is fair to say this is a very unusual situation. The last thing we want is for a very rare and unusual event to be creating alarm."
The four patients with symptoms of listeria went to hospital on May 9 and 18, and June 21 and 29. The two women, one in her 60s and one her 80s were "immune-compromised" and died within a week to ten days, said Hawkes Bay DHB's director of population health, Dr Caroline McElnay.
Infectious diseases physician Dr Andrew Burns said one woman definitely died from listeria, and it was a significant factor in the death of the other.
Dr McElnay said test results received on Monday showed three different "strands" of the disease in the four patients, and the women who died had different strands.
"For us to get four cases over a period of two months is really, really unusual," she said. "When you have a suspected cluster of listeria outbreak, the most likely cause would be a food source."
New Zealand had only about 25 cases of the disease a year.
The Ministry for Primary Industries has started an investigation which is looking at the "internal processes" of the hospital's food supply.
"We have identified listeria with products sold to us," Dr McElnay said.
She said the board was not buying any more ready-to-eat meat products - "we are cooking meat and slicing it ourselves".
The ministry's general compliance and response deputy director, Andrew Coleman, said the government body was overseeing Bay Cuisine's voluntary recall.
Asked why it had taken from Monday until yesterday to let the public know about the outbreak, Dr Snee said: "We got the results on Monday and were considering them over the next 24 hours and now we are here. I think that is not a long time."
Dr Burns said symptoms of listeria took up to 70 days to appear, and it was therefore harder to find its cause than the cause of other types of food poisoning.
The health board said listeria was dangerous only to pregnant women, their babies, the elderly and people with a lowered immune system. Bay Cuisine joint managing director Simon Wills said last night he was "extremely concerned" about the situation.
"As a precautionary measure, we felt it best to recall all products in the market until our investigations are complete," he said.
"Currently, we are waiting on the results of an independent review of our food preparation procedures."
He expected the recall would be completed within days.
Mad Butcher owner Mike Morton said only a minimal amount of product had been recalled from his stores, and it was not confirmed that it was infected.