Whitestone Cheese announced yesterday the recall of some of its Windsor Blue cheese, three weeks after the bacteria listeria was found to have contaminated the product.
But the Ministry for Primary Industries (MPI) said it was satisfied the public was informed as soon as possible.
Whitestone chief executive Simon Berry said surface contamination was detected in the factory's blue maturation room on February 12.
The company's MPI-certified auditors were notified on the same day.
''On January 31 we had some contractors in working on a chiller and we believe they had contamination in there and it got on to some products,'' Mr Berry said.
''At the moment we have had three batches that have tested positive, so subsequently we decided on a recall of five [batches] as a precaution.''
Mr Berry said all products tested had been held and re-tested. Further positive results were found on February 26.
''As a result of those tests we have gone through, we tested a wide net. We went through all our products, our entire products on site.
''We did 370 tests and they have all come back clear, with the exception of some Windsor Blue batches.''
He said all stores had been contacted and the company was issuing information for consumers.
About 500kg of cheese was being returned.
''We know every store location that it has gone to, and now we are working through contacting all those stores to get it off the shelves.
''We're very confident in our robust systems, and we have been working closely with MPI all through this.''
Mr Berry said the first product recall was issued on March 1 and further notices were issued in all major newspapers on Thursday.
He said he was happy there had been no delay in informing stores or the public.
MPI operational co-ordination manager Gary Orr said the ministry was told on February 26 and staff had been working with Whitestone Cheese since then.
''As soon as MPI was notified of this test result on February 26, we required the company to identify and hold all potentially affected product, both at their site and through their distributors,'' Mr Orr said.
''Whitestone Cheese initiated a trade withdrawal of positive product at 8pm that night.
''This action kept the majority of the potentially affected product away from consumers. Further testing was conducted to determine whether other batches were affected.''
Mr Orr said recall notices would run in daily newspapers tomorrow and on Monday.
A review of the events in the lead-up to when MPI was notified was under way.
Labour Party primary industries spokesman Damien O'Connor said while ''any delays are of concern'', it was not clear if those delays were at the testing level ''or within the bureaucracy of MPI''.
Products recalled included Windsor Blue 220g wedge with a best-before date of July 12, Windsor Blue 110g wedge (July 4, 6 and 13) and Whitestone Blue 4 cheese platter (July 5).
The products were sold throughout New Zealand.
No illness associated with the products has been reported. For further information, phone 0800-892-43373.
Listeria
• A food-borne bacteria that can lead to people contracting listeriosis.
• Listeriosis has few or no symptoms in healthy adults or children, but older people, pregnant women and people with weakened immune systems are at a higher risk of severe disease.
• Can cause miscarriage, premature labour or stillbirth.
• Symptoms include mild fever, headache, aches and pains, nausea, vomiting or diarrhoea, and stomach cramps.
• Symptoms can take a few days or weeks to appear after eating contaminated food.
