Parts of Hamilton's main street were closed earlier as seven fire appliances and police cars converged on the scene in response to an emergency incident, initially thought to be a fire.
A firefighter told the Herald a fire was believed to have broken out in level 7 of the Westpac Building near the corner of Victoria St and Alma St.
It was thought to have started in an air conditioning unit.
Hamilton Senior Station Officer Shane Thompson said they were called out to smoke showing on the seventh floor of the Westpac building about 3.45pm.
As there were reports of smoke, the call was put out for more resources as a second alarm, meaning extra fire trucks from around the city and beyond.