One of the men working on an upper level of the New Zealand International Convention Centre building site at SkyCity says a crane operator working above the roof was among the first to spot the burgeoning fire and raise the alarm.
Craig Merz was part of a team installing a building maintenance unit on an area between levels five and six of the seven-storey building.
He was waiting for the crane to swing the next load their way when instead the operator started sounding his emergency horn.
"We looked up to see what was going on - he pointed behind us and we saw rolls of black smoke. I said 'Ross, we gotta get outta here now'."