An inquiry into the gastro outbreak in Hawke's Bay may consider chlorination of all tap water in New Zealand.
It follows calls from a water safety engineer who says an event of this scale was always going to happen.
Water treatment engineer Iain Rabbitts says it could have been prevented if the water had been chlorinated.
"I am furious," he says. "I am absolutely ropeable about this. We knew it was going to happen; we knew it would happen at some point. We didn't know where and we're lucky it's such a small community.
"It just makes me so angry that we let it happen and we let it happen because the standards let us do it. The standards and the health acts let us do it."
Mr Rabbitts says all tap water in New Zealand needs to be chlorinated.
The Institute Of Environmental Science And Research, who advises the Ministry of Health, says currently 15 percent of New Zealand's population has unchlorinated tap water.
Today Acting Minister for Health Sam Lotu-Iiga was in Havelock North as the Government and the Hastings District Council work out terms of reference for a government inquiry.
He says the issue of whether to chlorinate all New Zealand tap water is something the inquiry may look at.
"We'll assess that decision if it has to be made, but right now it's about finding out what went wrong here before you can make a blanket statement about the position around unchlorinated water."
It was announced on Wednesday all primary and intermediate schools in Havelock North will be closed until Monday, August 22.
However, secondary schools Woodford House, Iona College and Havelock North High School have decided to open on Thursday, August 18.
One in two households in Havelock North have been struck down with the bug after testing on Friday picked up campylobacter in the water supply.
In total 3200 people have been affected, including nearly two dozen who ended up in hospital, two critically ill.
Claims that Hastings District Council knew water was contaminated days before a gastro outbreak in Havelock North are false and unhelpful, the mayor says.
Hastings mayor Lawrence Yule said water tests on Friday morning picked up something suspicious, the water was chlorinated by 5:30pm and the bug dead through the whole system by 8pm.
"It's completely unhelpful for people to be saying we knew about this earlier," he said.
"Any speculation we knew earlier, or that we knew Tuesday or Wednesday, is completely false."
The latest figures, following phone surveys and door knocking, show around 3200 people have fallen ill since Friday.
"This has never happened in New Zealand before so it's a major national incident," Mr Yule said.
Daily water testing is still underway and some bacteria is still being recorded in bore two, but tests of water once it has been chlorinated are clear, according to council staff.
Hawke's Bay District Health Board medical officer Nick Jones said action had been taken to fix the water quicker than national drinking water standards required.
"Because we had a hunch there was something going on ... we thought we were sufficiently concerned there may be something going on there," he told reporters on Wednesday.
"I'm absolutely convinced that saved a lot of people's health."
Officials believe the health system is coping well with the unprecedented outbreak but are continuing to urge people to be vigilant about washing their hands.
Dr Jones said people should wash their hands before and after preparing food, after going to the toilet or changing a baby's nappy, after caring for people with campylobacter and after contact with animals.
While campylobacter can't be spread through the air, it can be spread by swallowing the bacteria, through either contaminated water and food, or contact with infected people.
The notice to boil water will also remain in place until authorities are confident there is no other bug resistant to chlorination in the water.
Mr Lotu-liga is in Hawke's Bay to support the Hastings District Council and help set up an inquiry into the cause of catastrophe.
"We're working alongside the District Council, we need a level of independence, the belief there is that there'll be a retired High Court judge."
"Certainly one of the key questions is what do we do in order for this not to happen again?"
He wouldn't speculate on whether a decision will be made to chlorinate all water supplies in New Zealand.
"First we'll look at what went wrong, in this particular instance, then we'll look at the implications for this case on the wider supply of drinking water to all New Zealanders."
"We're not happy about 3000 people being sick, no one should be. That's the priority right now – to get people in Havelock North back to full health and well-being. The questions around what went wrong we'll need to inspect in due course and the inquiry will do that."
Red Cross and Civil Defence visited more than 400 homes on Tuesday, distributing emergency supplies.
Welfare control officer Alison Banks says teams are prioritising their efforts to the worst-affected areas.
"We're probably not going to get to every single resident in the community - we are using other mechanisms for that. We've got a team on the phone lines ringing over 700 of our elderly community members."
Auckland grandmother Jill Perrott is in Hawke's Bay helping her family deal with the crisis. She says the visit is a "mercy dash".
"It's quite catastrophic for many – kids, businesses, families… I have two sons in Havelock North, both with wives and three children apiece and all of the children have gone down with the bug, apart from one granddaughter, and one parent has gone down as well."
She says fortunately one the families lives out beyond the town water supply with their own bore, but the kids were poisoned by drinking from the school fountains.
NZN / Newshub.