Hundreds of people have fallen ill because of tainted tap water in a small town on New Zealand's North Island.
Schools were forced to close because of the outbreak in Havelock North.
Health officials said on Monday that two patients were in a critical condition and 19 others remained in a local hospital after testing positive for the campylobacter bacteria.
Anna Kirk, a spokeswoman for the Hawke's Bay District Health Board, said the death of an elderly woman at a nursing home was also being investigated, although it was not yet clear if she had contracted the illness.
Ms Kirk said at least 200 people have been treated by local doctors over recent days and that officials estimate up to 2,000 people have been taken ill.
Campylobacter bacteria are typically spread from animal faeces. Officials say they do not know yet how the underground water aquifers that supply the town became contaminated.
A bacterial outbreak on the scale of that in Havelock North is relatively rare in New Zealand, which markets its clean, green image to tourists.
New Zealand Prime Minister John Key said on Monday that the situation was unacceptable and it was clear a large amount of material needed to get into the water supply for it to become so contaminated.
"Fundamentally, we need to understand how it took place," he said.
Officials said they have been treating the water with chlorine and are also urging residents to boil tap water and wash their hands thoroughly. The town has trucked in tankers of fresh water.
Symptoms of those who have ingested the bacteria include diarrhoea, vomiting and fever. Elderly people and children are particularly vulnerable.
Five local schools decided to close for the next two days, saying about half the children were sick as well as many of the teachers.
About 13,000 people live in Havelock North, in a region that is known for its vineyards.