Hawke's Bay District Health Board has admitted it failed to test hospital food for listeria, despite four patients becoming ill with the bug and two of them dying.
The DHB says two patients at Hawke's Bay Hospital died after getting listeria, both of them older women who had compromised immune systems.
Two others, also older people with compromised immune systems, who had used hospital services also got listeria but have since recovered.
The cases were confirmed in May and June but processed meat such as salami, ham and pepperoni - which are known as sources of listeria - were not removed from the hospital menu until 10 July.
The DHB has confirmed the meat had signs of contamination, but won't say if it was the source of the outbreak.
Director of population health, Caroline McElnay, told Checkpoint the food wasn't tested because staff did not suspect the bug was in it.
Dr McElnay says in hindsight the hospital could have withdrawn the meats as a precaution after the first patient caught the bug.
She says the hospital is considering leaving processed meat off its menu permanently.
Hope outbreak over
Food safety officials say they hope the outbreak is over.
The DHB says the first of the four cases was notified in early May and the last on 29 June.
The Ministry of Primary Industries is seeking to identify the source and the extent of the outbreak.
Its deputy director general of compliance and response, Andrew Coleman, says he hopes it won't go further than the hospital.
"At this stage it doesn't seem that it will be much broader. There's certainly been no unfortunate deaths and illnesses through the Hawke's Bay District Health Board's hospital since the June date."
The DHB says investigations are still underway and it's too soon to say how the patients got the bacterium, but food's a likely source.
Pregnant women, the elderly and those with weakened immune systems are warned to be careful what foods they eat. They are advised to avoid soft cheeses, processed meats and poultry.
Family doctors say people who are generally well have nothing to fear from the outbreak.
Meat products recalled voluntarily
The ministry says it has overseen a voluntary recall of a number of ready-to-eat meat products.
At this stage the ministry says there is only one firm involved in its inquiry into the outbreak.
Bay Cuisine of Napier supplied ready-to-eat meat products to the hospital, but the ministry says it's not clear yet if any of these products are linked to the cases.
The ministry says it's talking only to Bay Cuisine, the board's sole supplier of packed meats, at this stage but may talk to other companies.
Bay Cuisine makes statement
Bay Cuisine hasn't been available for interview.
But in a statement, it says it's concerned about the outbreak and two deaths.
It says it understands the source of the contamination is yet to be determined and it's working with authorities to find the source.
It says it recalled products sold in Mad Butcher stores throughout the country and in Preston's stores in Wellington, Porirua and Palmerston North although none has shown any evidence of contamination.