Smoke rises from a gold mine on New Zealand's north island.

A blaze broke out underground in the Waihi Trio mine in the early hours of the morning, trapping 28 workers.

Operations were halted as the miners made their way to refuge chambers equipped with water, power and air.

Newmont Mining Corp, the world's second-largest gold producer, said it took seven hours to rescue all 28 workers.

(SOUNDBITE) (English) GENERAL MANAGER OF NEWMONT MINING, GLEN GRINDLAY, SAYING:

"We do not yet know what triggered the fire. It started on an underground truck, a Camacho 30 tonne truck. This will obviously be the focus of our investigation at a later stage. Our initial focus was ensuring the safety of all personnel on the mine and eliminating the fire hazard. All operations at the Trio mine and our other Waihi mining operations were stopped immediately."

The mining firm said none of the miners were hurt in the incident.

The workers were reportedly in good spirits after the rescue, with some initially thinking the emergency was a drill.

Sarah Charlton, Reuters.