Loud beeps sounded off across the country during a nationwide Civil Defence test tonight.
Texts were sent to about three million cellphones between 6pm and 7pm tonight, carrying the annual test alert message from the emergency system.
Ministry of Civil Defence and Emergency director Sarah Stuart-Black said the system was a vital information channel for warning people if their life, health or property was in danger.
People whose phones are capable of receiving alerts heard a loud sound when the test happened.
The alert test in November last year reached about a third of mobile phone users.
Ms Stuart-Black said the aim of tonight's test was to reach 50 percent of mobile phone users.
"People upgrade their phones, so over time we will see an increasing number of people able to receive those messages," she said.
The emergency alert system has been used five times since it was launched, warning people about problems such as a chemical spill, flying debris and water contamination.
Ms Stuart-Black said not all mobile phones would receive alerts, so people should check in with their neighbours to see if they got the message.