Public health officials are bracing for more cases of Legionnaire's Disease in Auckland.
Three new cases were notified over the weekend, bringing the total over the past nine weeks to 15.
One person has died.
Dr Simon Baker says the latest cases are in the Waitemata District Health Board area.
"We're still very much looking for the source but the fact that the cases have been spread all over the region means it's probably more than one source and it's going to be extremely difficult to tie down."
Dr Baker says the only way to stop the spread of the legionella bacteria is for all building owners to shock-dose their cooling towers.