The St John Ambulance Service is investigating whether the use of a new procedure for handling 111 calls delayed ambulances at the height of swine flu.
The organisation runs emergency ambulance communications centres throughout New Zealand and says it adopted an internationally recognised way of assessing flu-related calls in Auckland, Wellington and Christchurch.
St John says a new manual protocol was added to regular computer-based procedures in mid-July to handle a dramatic increase in demand for ambulances from callers suffering from the flu.
But by late July, concerns were raised about the priority given to cases under the special protocol, and its use was ended.
The new system was used when answering just over 1000 cases. St John medical director Tony Smith says seven cases are of particular concern, and three of these involved patients who subsequently died.
The organisation is stressing there is no information yet showing that the deaths had anything to do with the new procedure's use.