A Timaru raw milk supplier is being blamed for an outbreak of the bacteria campylobacter.
Seven cases have been confirmed in those who purchased milk from Timaru Village Milk, but South Canterbury Medical Officer of Health Dr Daniel Williams said that number could be just the "tip of the iceberg".
Village Milk shut its doors on Wednesday, awaiting more test results, and its franchisees have apologised.
Stu and Andrea Weir said correct procedure was not followed. New cows were introduced to the herd prematurely when test results showed contaminants were present. The affected batch of milk was sold over March 7 and 8.
"We let people down by not carrying out procedures properly; it's a bit disappointing," Mr Weir said.
The Weirs started selling raw milk from their Fairview Rd farm in mid-February to meet local demand.
Though they claim raw milk is a completely safe product when procedures are followed, the medical profession and Ministry of Primary Industries (MPI) disagree.
"Drinking raw milk is risky for your health," Dr Williams said.
"It can contain disease-causing bacteria and other organisms which can lead to gastroenteritis and other illnesses, some of which can be life-threatening."
The young, elderly, pregnant women and people with weakened immune systems were at greatest risk, he said.
Consumers can reduce the risk of getting sick from drinking raw milk by heating it up to 70C for one minute, or to 63C for 30 minutes.
Public Health Ministry for Primary Industries principal adviser Dr Craig Thornley said there was always a risk with raw milk, "even when stringent control measures are followed".
MPI works to identify the source of any contamination and with the producer to reduce the risk in the future.
Village Milk chief executive Mark Houston said the company had very high test standards and its procedures worked well.
It has six outlets nationwide.
The Timaru outbreak was the first to result in people getting sick through Village Milk products that he knew of.
New Zealand legislation allows producers to sell up to five litres of raw milk daily at the farm gate to buyers who purchase it for themselves or their families.
The Weirs service 100 customers a day, who buy up to 300 litres.
Ministry of Health data shows there were five disease outbreaks due to raw milk consumption between 2007 and 2009, as against 16 in 2010 to 2012.
The amount of raw milk sold in New Zealand is unknown, but according to MPI, research suggests between 1 and 3 per cent of the population consume it.
- The Timaru Herald