The Fire Service evacuated a building in central Invercargill this afternoon after a chemical spill earlier in the day.
Southland area commander Bruce Stubbs said a staff member spilt chlorine while mixing chemicals at the Blue River Dairy this morning.
Hours later, the worker started to feel unwell and an ambulance was called.
Mr Stubbs said another staff member from the plant - which produces sheep milk powder - was taken to Southland Hospital as a precaution.
He said fire crews evacuated the building shortly before 3pm and used special equipment to check whether chlorine was still present.
Mr Stubbs said the site no longer posed a risk but the owners would ventilate the building overnight.