Lake Wakatipu is used for Queenstown's town water supply. Photo: RNZ / Marika Khabazi
Te Whatu Ora says the source of the cryptosporidium outbreak in Queenstown was most likely human faecal contamination of the water supply.
It follows a detailed investigation.
Te Whatu Ora said based on all the gathered information to date, its most likely hypothesis was that the outbreak started through human faecal contamination of the source water in Lake Wakatipu, which has then been collected into the Two-Mile water treatment plant's intake pipes, then moved into the water reservoir.
"From there, it has then been distributed around the Two-Mile water distribution network to homes and businesses, most likely over a number of days."
They say the contamination could have been from swimmers, sewage from a boat, wastewater overflows or other faults in the system.
Previously, officials were unsure the source would ever be known.
There have been about 60 cases of cryptosporidium confirmed in the area in the past few weeks.
People living in Hanleys Farm, Kelvin Heights and the Frankton flats area can drink straight from the tap again after the drinking water regulator, Taumata Arowai, said on Thursday the council could lift the boil water notice for the area served by the Kelvin Heights plant.
However, the boil water notice is still in force for residents served by the Two Mile plant, which includes Queenstown CBD, Fernhill, and Sunshine Bay.
More to come...