Waikato District Mayor Allan Sanson says a Mt Eden prisoner should never have been bailed outside Auckland to the area where cases of Covid-19 have now been discovered.
The three cases in the Firth of Thames household are contacts of the man who spent more than a week there on electronically-monitored bail.
The infections were discovered after the man returned to prison in Auckland and tested positive for the virus.
Sanson told Morning Report it was "totally irresponsible" to send a prisoner on bail outside the lockdown boundary and into the small community.
"There needs to be questions asked as to why it actually happened.
"I would have thought if you were bailing somebody you would have bailed them into Auckland, and not out of the Auckland area.
"They don't let anyone else out of Auckland into a level 2 area without them having tests now, so what's the difference with this? This person's been in the community for well over a week."
He said it was devastating for a tight-knit rural community.
"They very much stick together, and to have something like this imported into the community is going to be a real blow for them."
Two of the new cases are children who went to Mangatangi School and at least one was symptomatic while there, the Ministry of Health has said. All three were being moved to a quarantine facility.
Sanson feared there would be spread of the virus given the students attended the school of more than 100 pupils last Thursday.
Hauraki District Mayor Toby Adams is disappointed the family are already getting abuse from some members of the community.
"I'm hearing words on the street that the community is a little bit up in arms and giving the family a bit of grief."
There would be anxiety about how far cases might have spread, he said.
"We're in level 2 so people are allowed to move about, so lets just hope people have been using the Covid app and logging in where they've been and wearing their masks.
"I'd be pretty surprised if there was not another case."