Major disruptions in Auckland after a blaze has roared through the roof of the Sky City Convention Centre, which is under construction

It began about 1pm and has led SkyCity to evacuate all its buildings - including Sky Tower, its hotels and nearby restaurants

Reporter Lucy Thomson says firefighters have no clue how it started - but say it's the least of their worries while they try to get the fire under control.

She says streets have been cordoned off and it's not easy for emergency staff as the wind changes direction.