A water assessor says no tankers have been found to be contaminated with E. coli, after fears were raised when an 'indicator' of the bacteria was found in water supplied to Havelock North.
The tanker was one of nine sent to Havelock North from Hastings after a major gastro bug outbreak, which came from the Hawke's Bay town's water supply.
Hawke's Bay health protection officer Peter Ward said appropriate checks have been carried out, and there are signs that the reading may have been false.
"We'd still need to do the investigation into this particular event, [but] we have got good records from our registered tankers that show they have been operating effectively," he said.
"We will continue to assess the information as it comes in."
In a press conference, Mr Ward explained that it's very difficult to get a sterile sample out of water tankers, and because of that it is not out of the ordinary to have low counts of bacteria.
He said the water tankers collect from the main Hastings water supply, which has had no issues over the past 12 months.
Hawke's Bay District Health Board chief executive Dr Kevin Snee said the necessary precautions would be taken to prevent ingested camylobacter or E. coli simply by drinking water.
"There is no evidence that the water supply in Hastings is contaminated. What we have here, probably, is a contamination of the tanker - but in the circumstances that we're in, the council are being very careful and are chlorinating the water supply," he said.
Dr Snee said there were obvious signs of improvement in regard to the region's gastro outbreak.
"From a health system point of view, it's quite reassuring what we've seen. The pressure in the system has been less. [In] primary care, in St Johns and in pharmacy it seems to be under control," he said.
He says what has been most encouraging is that there has been a reduction in new cases over the past few days, and that the health system has coped with the influx of patients.
There are still 17 people in hospital with gastro, one of which is in intensive care in a stable condition.
Auckland Regional Public Health Service medical officer, Dr David Sinclair, says Hawke's Bay Regional Council will give Hastings residents the green light to drink water from the local supply later on Thursday.
The wait will allow chlorine to flush completely through the water systems, Dr Sinclair said.
He said there's "myriad possibilities" of what could have caused the contamination of the tanker.
Dr Sinclair said there was no indication from tests that any patients had been treated for an E. coli-related disease - a result he described as "reassuring".
The council is now determining whether it should close the current bores its sourcing water from, which link back to the Hastings water system.
In response to criticism of the council's sluggish reaction to the gastro outbreak, Dr Snee said the Hawke's Bay DHB actually acted fairly quickly.
He said their attempts to contact the community on a Friday night were "not necessarily as easy as it might be at other times of the day".
"We took a decision that the most efficient way to do that would be to go through various media, which is probably more efficient than going and knocking on people's doors," he said.
"At the time we weren't really sure what was going on - we were operating on a suspicion having put some evidence together, and it sadly proved to be the case."
Dr Snee said nursing homes would be properly supported in the coming days.