The Hastings District Council admits communication could have been better, following the outbreak of a gastro bug in Havelock North.
Schools were closed on Friday as hundreds of people fell sick with a stomach bug, but residents feel the spread could have been contained.
Hastings mayor Lawrence Yule says e-coli entered the town's water supply between the twice-a-week testing regime.
"My councillors and myself are pretty distressed that a whole group of our community have been taken down with a pretty nasty bug, from a water supply that we are charged with providing them.
"At the moment we can't explain how it has happened but it's certainly happened and we need to get to the bottom of it and resolve it quickly so that it doesn't happen again."
Lawrence Yule insists action was taken as soon as testing confirmed contaminants were present..
Havelock North resident Lucy Dobbs said it hit her community hard.
"Everyone has it to varying degrees, my friend's son has been curled up on the floor in a ball all night he's so bad."
She said lack of communication from the council was "appalling".
"I knew through friends at the hospital it was bad but it's been 'Chinese whispers', it wasn't until this weekend the councils finally put something on the website."
Others shared thoughts online, asking if the Hastings District Council kept quiet on the problem because of looming local government elections.
On Facebook, Roger Corbett wrote: "Many residents are feeling that District Council and the DHB should, on completion of their investigations, provide an explanation for their slow reaction to this event. Perhaps they will wait until after the imminent local body elections?"