Eastern Bay of Plenty Civil Defence is working to get to the bottom of last night's tsunami false alert and is giving the matter the highest priority.

The tsunami alert sounded for about seven minutes at 8pm on Monday with sirens heard in Whakatane, Opotiki, Matata, Coastlands, Ohiwa, Waiotahi and Waihau Bay, but it appears that the siren did not sound in Ohope.

No tsunamis were detected in the Eastern Bay of Plenty overnight. Photo: File.

A previous false alert occurred in September and following an investigation, a software fault was found to be the cause of the issue.

Eastern Bay of Plenty Emergency Management coordinator Jim Tetlow says the matter is under urgent investigation with alarm company Kordia, but the Civil Defence team is still unsure what caused the issue.

'Following the September false alert, additional security measures were put in place to prevent another occurrence. Unfortunately, last night the alert system sounded again last night without being intentionally activated by Civil Defence.

'We are investigating the cause of the activation with our provider, Kordia, and will update the public on the cause as soon as it is understood.”

Opotiki Mayor John Forbes says the main concern is people losing faith in the system.

'During this activation, many more people did the right thing – they tuned in to their radio to 1XXand listened for updates and to find out more. 1XX was prompt in supplying the information to the public as well.

'But I appreciate there is a high risk that people will stop paying attention to the alerts and this is a concern for Civil Defence. It's possible that there will be further issues before the root cause of this problem is found, but I encourage people to continue to treat the sirens as they are intended – as a warning signal to find out more about the situation.”

Jim agrees before emphasising the alert sirens are only part of the picture.

'People need to understand what the natural warning signs of a tsunami threat are. If there is a large earthquake that you cannot stand up in, or the shaking goes on for more than a minute, this is a natural warning of a potential tsunami. In those circumstances, people in coastal areas should not wait for an official warning and should move immediately to higher ground or inland,” says Jim.

Investigations are continuing and updates will be provided when further detail s are known.