Fire and Emergency senior station officer Phil Grace told RNZ most of the road has been blocked off while they respond.
It was unsafe to have vehicles driving while they had firefighters and hoses on the road.
When their crews first arrived at the scene there was a lot of smoke coming out of the ground level of the building, he said.
Alan from the Salvation Army Family Store on Dominion Rd said workers noticed the fire at a neighbouring building after 1.40pm.
“There’s been thick, black, billowing smoke coming out of the front door … we’ve had to close our store.”
He said the affected building was previously used by Gumboot Friday and was set to be demolished.