Four dairy herds in Taranaki are infected with bovine tuberculosis.
Taranaki has been considered free of Bovine TB for a number of years although experienced a small outbreak in 2008 and 2009.
TBFree New Zealand said the infected herds, one near Opunake in South Taranaki and three near Inglewood, are being carefully monitored to prevent the disease spreading.
Animal Health Board regional co-ordinator Frank Pavitt said the outbreak started at the end of last year and has continued this year.
He said the infected Opunake herd is in the same area as the outbreak several years ago, but there is no direct link at this stage.
Mr Pavitt said stock movements in the infected properties are being investigated to find the source of the disease.