A man has been taken to hospital after a refrigerant leak at the former Telecom exchange building in central Wellington.
Firefighters were called to the building on Cambridge Tce after an alarm shortly before 4pm, Fire Service central communications shift manager Mike Wanoa said.
"Upon arrival we found it was leaking refrigerant gas, in which case the whole building had to be evacuated."
One person suffered minor injuries after inhaling the gas and was taken to Wellington Hospital as a precaution, an ambulance spokeswoman said.
Six fire crews and specialist hazard units were still at the scene.
Mr Wanoa said the situation was stable and the gas was being contained.
Health and safety inspectors and pollution response teams have been called to the scene.