Police have asked New Zealand's media outlets to delete any sensitive personal information emailed by the cyberattackers who claim they downed the Waikato DHB 's systems.
The DHB's systems have been out since last week after a ransomware attack.
Media organisations - including RNZ - were sent an email on Monday which apparently contained sensitive DHB data.
Waikato DHB chief executive Kevin Snee has now confirmed the files appear to be genuine.
Police have opened a criminal investigation and have asked media to delete any downloaded files.
RNZ is considering the request.
Earlier, DHB chief executive Kevin Snee said they were examining the files to identify the individuals affected.
"We'll be making contact with those individuals when this has been completed to meet our obligations of notification and to provide support."
Snee said they would contact those people in the next day or so, but asked everyone to stay alert.
"The public are being reminded to remain vigilant and to be particularly wary at this time of any unsolicited communications claiming to be from Waikato DHB, a government organisation or private companies."