Health officials believe the gastro bug that has made thousands of Havelock North residents badly ill has peaked.
Prime Minister John Key this morning met with the director-general of health and other officials over the outbreak.
Schools have been closed and hundreds are still house-bound, suffering aches, pains, vomiting and diarrhoea caused by water contamination.
Residents were alerted on Friday to begin boiling water for a minute before drinking.
But there has been widespread frustration and anger, with some questioning how quickly and effectively the council acted.
Key said the Ministry of Health would be involved in an inquiry that would be run by the council and likely to be led by an independent judge.
"People need to be able to feel confident. Ultimately a couple of thousand people and people seriously ill in hospital is not acceptable.
"The best advice we have at the moment is about 2000 people are likely to have been affected, there are a couple of dozen in hospital."
Local and National MP Craig Foss said people had raised concerns about the council's actions with him.
"They are just simply frustrated - how can this be, how come it took so long for us to understand.
"It is specifically the Hastings District Council responsible for water. But people have also come to me with their frustrations about how we ended up where we are."
Foss attended this morning's meeting and was advised the District Health Board had the resources to cope with the outbreak. Campylobacter bacteria was suspected and those affected generally needed to rehydrate and rest.
"The DHB believe it has peaked yesterday and hopefully today with the incubation period...but that remains to be seen."
Stuart Nash, Labour MP and representative of the neighbouring Napier electorate, said the outbreak was a "disaster".
"We are talking about kids that can't go to school, we are talking about one person that has died, we are talking about possibly the largest public health disaster in a generation - and the Government has been missing in action.
"And I think from a communication perspective it really has been a lesson in how to not handle a disaster.
"I don't know if the Government should be coming in over the council, but they certainly should be working very closely with the council."
Nash said he had no doubt that poor communications had cost people their health.
"I have talked to friends in Havelock North - they haven't been knocking on the doors of everyone over the age of 75 to see if they are okay."
Hastings District Mayor Lawrence Yule has publicly apologised to residents and promised the inquiry would find out exactly what happened.
He told Radio New Zealand that he was told about the contamination about 3.30pm on Friday and a decision was made then to chlorinate the water.
There had been a suspicious test about five hours earlier, he said, but the council needed to be sure something was wrong.