Six people in Christchurch have contracted the potentially fatal legionnaires' disease, and the source of some of the cases is yet to be confirmed.
The Canterbury District Health Board's Medical Officer of Health, Ramon Pink, said the six people were now fully recovered, but all needed to be treated in hospital.
Dr Pink said they believe a cooling tower in Woolston was responsible for four of the people's illnesses, but two other cases were notified after that cooling tower was treated in April.
He said the appearance of two more cases in May, indicated the treated cooling tower had already infected another tower, or that it was not the starting point of the infection.
Three of the people infected live in the Woolston area, two are regular visitors to the area, and one works in the business where the contaminated cooling tower was found.
Dr Pink said they had been in touch with businesses in the Woolston area with cooling towers, and asked them to test and treat their towers, and there have been no new cases for three weeks.
However the source of the other two infections has not been determined.
Dr Pink said symptoms of legionnaires' disease include a fever, headache and muscle aches.
He said if people were concerned that they may have contracted legionnaires' they should contact their doctor.
Dr Pink said there was no need to avoid the area near the contaminated cooling tower, and the risk to anyone living and working in the area was very low.