A siren that sent some Bay of Plenty residents fleeing for higher ground was due to a "forgotten" system that has now been disabled.

The sirens were activated on January 19 about 9.15pm, particularly around Waikato and Bay of Plenty and were a false alarm.

While there was no actual threat, many people took the sirens to be a tsunami warning.

Fire and Emergency NZ region manager David Guard and Bay of Plenty director of emergency management Clinton Naude said the sirens were from a redundant local tsunami alert system, which had not been used for about a decade.

While it had been overtaken by a national Civil Defence alert system, it had not been completely disabled and was triggered.

David said they patched the alert to stop any further activation of the siren and then took further action and disabled the system completely.

The old system, set up in 2006, allowed local Civil Defence to access and remotely activate fire station sirens and other sirens using the New Zealand Fire Service paging network.

Clinton said what happened on January 19 would not happen again.

Fire and Emergency NZ did not respond to questions about how the sirens were activated.

Clinton says within Bay of Plenty there are fixed sirens in Thornton, Whakatane, Ohope and Opotiki.

They were owned by the corresponding councils for the Whakatane and Opotiki districts.

He said the sirens heard on January 19 were a long consistent tone, making it unusual for the area.

Kirsty Lawrence/Stuff