Media company NZME says a hacker has managed to get access to the details of tens of thousands of people who entered a competition.
Initial investigation shows the information of 76,000 people was held on an overseas cloud server used by a business partner.
The details were primarily names, email addresses, phone numbers and some travel information.
In a story posted on the NZ Herald website, NZME Chief Executive Michael Boggs says there was no evidence the information had been used. It did not contain any credit card details.
Competition partners and those who had entered were being contacted.
''The priority for us is firstly security and secondly then making sure that they're not open to spam or phishing that could come from this," said Mr Boggs.
"We're continuing our investigations - we believe it would be an offshore person or persons involved.''
NZME publishes the New Zealand Herald, nzherald.co.nz, and owns radio stations including Newstalk ZB and ZM.
The media company says it has briefed the Privacy Commission.