Civil Defence says Northland Regional Council will investigate what accidentally set off a series of tsunami sirens in the area on Friday night.
The sirens went off shortly after 7pm, prompting a number of emergency calls from worried people.
Whangarei District Council recently installed 70 sirens along its eastern coastline from Bland Bay to Mangawhai to give early warning of a possible tidal wave.
Civil Defence spokesperson Adrian Prowse says it is not clear whether the false alarm was due to a software problem or human error.
"Clearly, there's been some form of technical glitch and unfortunately the sirens were inadvertently activated - and it's definitely a false alarm. There is no need for concern for Northland residents."
Mr Prowse says a planned test of the sirens will take place on Saturday morning.
A resident says the sirens panicked many people on a busy Friday night.
Council spokesperson Ann Midson says sirens will sound at 9.20am on Saturday and continue for 10 minutes.
The sirens will then flash blue lights and sound again for a couple of minutes at 10am.
Ms Midson says in some countries the tsunami sirens mean head for the hills - but in New Zealand, they mean people should turn on the radio for information about what is happening and what to do next.