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Another outbreak of the deadly listeria bacteria was revealed last night when public health officials confirmed infected sandwiches were sold to 20 people at Middlemore Hospital.
The pre-packaged Thai chicken sandwiches were sold on Monday at the hospital's Aviary Cafe, which is mainly used by staff.
The contamination was detected in routine testing, and the results were given to the hospital yesterday.
It was not known last night whether other sandwich varieties at the cafe were infected, or if other products from the sandwiches' supplier, Naturezone, were infected with listeria and had been distributed to other outlets.
The bacterium can be fatal to people with low immune systems and can cause miscarriages or stillbirths if it infects pregnant women.
A spokeswoman for Spotless Services, the company that runs the cafe, said it was not yet known how many of its outlets had been stocked with the sandwiches. Naturezone could not be reached for comment last night.
The outbreak follows discoveries of listeria in meat products from Leonard's Superior Smallgoods over the past two weeks.
Auckland Regional Public Health Service spokesman Dr Greg Simmons said last night that greatly improved methods of testing were bringing the listeria cases to the surface.
All positive tests in the past three weeks had come from the same testing facility.
"We are conducting a site inspection at the company concerned, and we will ensure extensive product and environmental testing," Dr Simmons said
Despite the relatively low risk, he said, it was a serious situation.
"We are concerned that a whole lot of ready-to-eat products look like they are being contaminated. We would be silly not to be concerned."
The bacterium usually produces fever, diarrhoea and general unwellness within three weeks of infection, although it can take as long as 10 weeks for symptoms to show.
