Water tests have been carried out regularly across Kawerau to monitor the quality of the town's water supply. Three days ago it tested positive for E. Coli, a bacteria commonly found in faeces.
Mayor Malcolm Campbell denied spoken suggestions the results were due to an ageing infrastructure.
"The most important thing is the test came about by normal sampling, it had positive reaction," Campbell said.
"It had nothing to do with daily basis, something has happened in the system and we are taking it very seriously."
The presence of E. Coli in the town's water supply meant residents were told to boil their water until further notice. That notice was lifted this afternoon.