The Ministry of Health says there may have been delays in diagnosing 28 women with breast cancer in Otago and Southland, after failures were uncovered in the breast screening service.
An urgent investigation is under way into failures in the BreastScreen HealthCare scheme serving women in the regions covered by the Southern District Health Board (SDHB).
An internal audit has identified that there may have been a delay in the diagnosis of breast cancer for 28 women over a three year period, where the mammograms may possibly have been misdiagnosed.
Ministry of Health chief medical officer Don Mackie said the issue was being taken seriously and an urgent investigation is under way by senior officials, the ministry and SDHB.
They hope to find out what went wrong and what actions need to be taken to rectify the issue.
"Additional checks are being set up at key steps in the screening and assessment pathway," Dr Mackie said.
"These include review by experienced breast screening radiologists who are external to Southern District Health Board."
Dr Mackie said the investigation was likely to prompt questions from the public about the programme - which was understandable.
He says he fully expects all the questions women will ask will be answered by the investigation.
"Unfortunately we won't know the answers just yet."
He says the Ministry's advice remains that the core breast screening programme is sound and that women's best protection against breast cancer - the most common cancer in New Zealand women - is regular mammograms through the programme.
The BreastScreen HealthCare scheme offers free regular mammograms to women aged 45-69.
Nationally, the programme screens 318,490 women every two years and detects 1900 cancers during that time.