Fire and Emergency NZ (Fenz) says last night's false-alarm tsunami alert in Bay of Plenty was a "legacy issue", while praising residents for evacuating.

About 9.30pm on Sunday sirens from Waihī to parts of Tauranga panicked residents who started evacuating thinking it was a tsunami warning.

National commander Kerry Gregory said Sunday night's false alarm was a "legacy issue".

"It is part of a system to alert the public.

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"The system also sat within surf lifesaving clubs, Fenz, the race park, and some fire stations was not necessarily ours.

"But that system is a legacy system, it is retired and not actually in place."

While they still did not know what caused the false alarm, and whether it was due to technical or human error, Fenz had put "patch" fixes in place until they figured out how to fix it long term, Gregory said.

Nine sirens tghat sounded were at fire stations, and three were not.

A Fire and Emergency spokesman declined to answer questions from the Herald about which stations the sirens sounded at, whether they were part of a current tsunami warning system and whether the same alarms would go off in an actual tsunami warning, and referred all queries to the local Civil Defence Emergency Management (CDEM) team.

The local CDEM has not responded to requests from NZME for comment.

Despite there being no real emergency, Gregory thanked those who took the alarms seriously.

"I would far rather people evacuate, than people don't take it seriously and we have a different situation."

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The system had been in place since 2006, he said.

As different groups amalgamated, the system sat there but people "forgot it was activated".

It was not activated by Fenz, but they did not know how it was activated at this stage.

"Have the confidence we will get our system right. If there is a siren, we want people to evacuate.

"We are taking this very seriously, working to find out the technical fix. Unless we know the detail behind what set this off, we are not going to be able to fix it long term."

They did not believe the system had been hacked.

Bay of Plenty residents were up in arms last night after the false alarm had them fleeing for higher ground fearing a tsunami, and want the system perfected before a real emergency strikes.

Chief executive Rhys Jones apologised on Monday morning, but could not say at this stage if it was human or a technical error.

Jones said their sirens were linked to a nationwide emergency alert system, and they would be working with their responding partners.

A spokesman for the National Emergeny Management Agency (Nema), which is responsible for issuing tsunami alerts, told the Herald it did not itself operate tsunami sirens, and last night's sirens had nothing to do with its own tsunami warning system.

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But residents have raised concerns about the confusion the false alarm caused, with many waiting to receive an official text alert from Nema, others not hearing the sirens at all, and the fate of people who did not have access to either phones or sirens.

Tauranga resident Brenda Newman, who evacuated with her family upon hearing the alarm, said there needed to be better alarm and alert systems for future emergencies - particularly making sure that everyone was alerted to a situation.

Although some people had chosen to evacuate, others were at a loss as to what they should do as they waited for instruction from a text alert or notification on their cell phone.

Other people, however, were unaware of the situation.

"It's pretty poor. They need to be accountable for this and just reassure everybody that they can sort something out for us," Newman said.

"There are so many elderly people who don't have phones - how would they know?"

Notification systems needed to take those kinds of factors into account, she said, suggesting maybe more sirens needed to be placed around the community so everyone could hear an alarm the next time it went off.

New Zealand's tsunami warning system

New Zealand's entire coast is at risk of tsunami.

A tsunami can violently flood coastlines, causing devastating property damage, injuries and loss of life.

Tsunami waves can smash into the shore like a wall of water, or move in as a fast-moving flood or tide.

New Zealand has experienced about 10 tsunamis higher than five metres since 1840.

Some were caused by distant earthquakes, but most by seafloor quakes not far off the coast.

Nema is responsible for issuing tsunami warnings.

Waihī Beach residents were in a panic last night after a false fire alarm had them thinking it was a tsunami warning. Photo / File
Waihī Beach residents were in a panic last night after a false fire alarm had them thinking it was a tsunami warning. Photo / File

In the event of an earthquake, the ministry uses information from its GNS Science partners to issue advisories to regional Civil Defence Emergency Management Groups (CDEM Groups), media, and the public, including through text messages.

The level of information will depend based on the distance of the earthquake from the coastline.

A tsunami coming from far away gives GNS Science more time to gather data and assess the tsunami's characteristics, and give a more accurate assessment.

Official warnings, through channels such as TV, radio, social media, apps, emergency phone alerts and sirens, are possible for distant and regional source tsunami, which may take hours to reach New Zealand and give GNS Science time for a more accurate assessment.

If an earthquake occurs close to the New Zealand coastline - such as in the Hikurangi, Kermadec, or Kaikoura trenches - a tsunami could arrive in minutes, meaning scientists do not have enough time to assess the threat, and Nema might not have enough time to issue an official warning before waves arrive.

In these situations Nema recommends communities act immediately, and people near the coast after a large, strongly-felt earthquake follow the advice: "long or strong, get gone".

This means people must move immediately to the nearest high ground or as far inland as they can if they are at the coast and feel a strong earthquake that makes it hard to stand up, or a weak rolling earthquake that lasts a minute or more; see a sudden rise or fall in sea level; or hear loud and unusual noises from the sea.

While the initial alert comes from the national body, each local CDEM group is responsible for how that message is relayed to its community, including whether it uses sirens.

A Nema spokesman said the mobile alert system was the closest New Zealand had to a nationwide siren system.

Sirens were used in some parts of the country, but that was up to local authorities to decide, he said.

In December, Foreign Affairs Minister Winston Peters and Civil Defence Minister Peeni Henare announced a new network of 15 Deep-ocean Assessment and Reporting of Tsunami (Dart) buoys to confirm the generation of tsunami waves before they reach the coast.

Henare said the programme would provide early detection and support warnings for tsunamis generated from the Kermadec and Hikurangi trenches.

"This system will provide rapid confirmation if a tsunami has been generated, and will enable more accurate warnings of tsunami that can be communicated via public alerting systems like Emergency Mobile Alert."

GNS Science's National Geohazards Monitoring Centre will support the 24/7 monitoring to receive, process and analyse the data from the buoys, and the National Emergency Management Agency would issue tsunami warnings and advisories to the New Zealand public.

The Dart buoy network will also provide tsunami monitoring and detection information for Pacific countries, including Tokelau, Niue, the Cook Islands, Tonga and Samoa.