Emergency Management officials are reviewing the mobile alert system after some residents reported being woken by repeated emergency messages following yesterday’s massive offshore earthquake.

The magnitude 8.8 earthquake struck near Russia’s Kamchatka Peninsula, prompting widespread tsunami warnings across coastal regions of New Zealand.

Emergency Mobile Alerts were sent to all coastal areas warning people to stay off beaches and away from marine areas due to the risk of strong and unpredictable surges.

A spokesperson said, “Thanks to everyone who followed the advice and stayed clear of the beach and coastal zones.”

However, the system is facing scrutiny after some people received an additional alert in the early hours of the morning.

“We are looking into why this happened and are sorry to anyone that was woken up by it,” the spokesperson said.

The system uses cell broadcast technology to send alerts through local towers. A technical glitch, combined with network changes such as moving between 3G and 4G, turning flight mode on and off, or rebooting phones during the broadcast period, may have caused extra alerts to be received.

In some cases, phones with an alert reminder setting switched on will repeat the alert until acknowledged. This setting can be turned off under “Wireless Alerts” or “Emergency Alerts” in phone settings.

Emergency Mobile Alerts are designed to warn of serious threats to life, health or property, and have been used in the past for tsunamis, fires, and severe weather events.

“While the sound can be alarming, it is based on an international standard chosen specifically to grab attention because it is unpleasant to the human ear,” the spokesperson said.

People can view alert messages again on their phones through the ‘Messages’ app for Android or the notification centre on iPhones. Once deleted, the alert cannot be recovered.

Authorities said people cannot opt out of the alerts, as they are designed to reach everyone in a targeted geographical area at risk.