The source of last year's water contamination in Havelock North, which killed three people and left 5000 violently ill, has finally been found.
Mangatareretere stream on the outskirts of Havelock North was the culprit, contaminating the town's water and prompting a gastro outbreak.
Hastings Mayor Lawrence Yule said the discovery has "completely unravelled the puzzle".
Scientists have found that back in August, sheep faeces from animals grazing in a paddock near the stream ran down into the pond, which would have been full of water at the time.
Then, over a number of hours, that contaminated water was sucked through the ground and into the town's water bore - about 80 metres up the road.
The theory was tested by putting green dye in the pond, which ended up in the bore after 29 hours.
The report by four scientists from regional and local councils is part of a government inquiry.
While the inquiry works toward more answers, the bore is being decommissioned and all Havelock North's water will come from another bore.
A $1 million UV filter will take over the job of keeping the water clean in a couple of weeks.
In 1998 there was an Ecoli outbreak in Havelock North. Scientists now suspect the same thing happened then, but councils didn't make the link.