Fire and Emergency has apologised to Bay of Plenty locals after a number of its sirens that went off last night prompted fear of a tsunami.
About 9.15pm, sirens sounded from Tauranga to Waihi with many members of the public taking them to be a tsunami warning.
Fire and Emergency chief executive Rhys Jones told Morning Report the fault which caused the error is not yet known and would be investigated.
"These false alarms are clearly what we don't want to happen, because ... we have to trust the system and we don't want to get into a 'cry wolf' situation where too many false alarms come through," Jones said.
"We're taking it seriously and we do apologise to all those who were affected."
He said those sirens can be connected into a regional emergency response system as well as nationwide civil defence alert system if needed.
It may have been a technical or a human error, he said.
"These alert systems need to be reliable and the public need to be able to trust that."
Waihi Beach resident Baz Dillimore said when the alarm did not stop quickly, he gathered his kids.
He said people evacuated calmly, some headed to the RSA up the hill and others sought higher ground.
"People are still I guess pretty much on edge with the White Island eruption not long ago, so people are very aware of that. I think it's better to have false warning than no warning at all."
Director of emergency management for Bay of Plenty, Clinton Naude, told Morning Report that Civil Defence did not have any sirens for the area where reports came in.
"We had some reports of some of them being potentially from Fire and Emergency New Zealand's fire brigade, who use siren networks to activate volunteers to callouts.
"But we've asked Fire and Emergency New Zealand to investigate and come back to us on what has happened there."
Naude said the tsunami and volunteer callout sirens had different networks and tones, but people have in the past confused the two.
"But last night's event was quite unprecedented with such a wide range of sirens going off at the same time."
He said he wanted to reinforce that the primary alert system for the Bay of Plenty, for tsunamis and serious events, was the mobile notification.
Naude also urged people to check multiple channels, like authorities on social media, radio and television broadcasts, because these were likely to contain more information if there was an emergency.