About 5000 households on the North Shore started their day thinking Sunday's tsunami warning was nothing more than a drill.
From 7am, a message was sent out to subscribers of the city council's automated phone tsunami warning system saying it was a practice call.
Glenn McDonald, of Campbells Bay, saidhe received the phone call about 7.30am saying it was a practice warning and to expect further details by phone, but those details never came.
He took the dog for a walk on the beach and did not turn on the television or radio before he left.
"We arrived at Mairangi Bay surf club to find the beach closed with a sign. We thought, 'They're taking this practice seriously'."
Returning to Campbells Bay, Mr McDonald said, there were no signs or indication that anything was wrong.
"We get home, go inside and the kids tell us it's for real."
Mr McDonald turned on the television to find out more, but the only broadcast they could find with information was Fox news.
Council spokesman Rob Pitney said once it was realised the wrong message had been sent, an updated call was made to the subscriber households, but he admits not all homes received it.
The Sunday alert was the first time that the warning system had been used in a "real life" situation.
Mr Pitney said an investigation into how the mistake occurred was under way.
The council set up the automated system after the 2004 Boxing Day tsunami. It is designed to send a recorded message to registered users in the event of a tsunami threat.
People living or working on land less than 15m above the low tide mark are encouraged to register. There are close to 5000 people on the alert database.
