Northland Civil Defence has apologised after a fault in its network caused tsunami sirens to blast through the Whangārei and Kaipara districts.
The false alarm came just ten days after a real tsunami threat forced evacuations across New Zealand.
Monday's alarm was the result of a "technical issue" in the control systems, Northland Civil Defence wrote on Facebook.
"We wholeheartedly apologise for this and the effect it had on people - we're very much aware of the responsibility that comes with the alerting platforms we manage.
Northpower, the company which installed and maintains the alarm system, also apologised, saying it is "fully investigating" exactly what happened.
"We are very sorry for scaring everyone with this false alarm. After last week's events we know this will have caused some concern."
Comments on the post said it was "not nice" to have heard the tsunami warnings again so soon after a series of earthquakes prompted a warning for great swathes of the country.
"That's a pretty stressful false alarm!" wrote one woman.
"At least we know it works! Got my elderly mother out of bed," wrote another.