The Eagle helicopter is circling overhead and ambulances are also there.
More police vehicles have been seen heading towards the area.
Police say the situation is currently contained to a building in lower Queen Street, which is under construction.
An RNZ reporter says police appear to be further extending the cordon.
The Fullers Ferry building is in lockdown and no ferries are arriving.
Reporter Felix Walton spoke to Ingrid Hipkiss from Queen Street.
