Earlier the Hastings District Council said an e-coli indicator has been found in one of nine water tankers used to supply drinking water to Havelock North residents.
David Sinclair, an Auckland medical officer of health, said council was considering connecting Havelock to Hastings water. The indicator test today "not unexpected" in such a situation, he said.
He said the health team have taken "a very professional approach" in handling the situation.
Dr Sinclair said that often large outbreaks were not apparent until they were well underway so he was not surprised the DHB ound out last Friday.
The council made the decision to chlorinate the water supply and emailed the DHB to tell them about it. The DHB confirmed chlorination today was appropriate, the council water services manager Brett Chapman said earlier
The suspect water tanker had a sign placed on it as soon as the positive indicator test was received and the tanker was later removed.
It had been at Havelock North High School car park since Monday.
Residents were directed to the tankers by the Hawke's Bay District Health Board after thousands became ill from campylobacter in the water last week.
Those who took water from the site and still have it in containers were asked to dump it.
All tankers were made vandal-proof.
The tanker had been filled up in Hastings. Hastings mayor Lawrence Yule said the decision had been made to chlorinate the Hastings water supply immediately as a precaution, despite the majority of indicator tests returning negative.
The water from the other tankers had been tested and was clear, however the water in all the tankers was now chlorinated.
