Forty staff from a Christchurch manufacturing plant needed medical care after a chemical spill.
The alarm was raised at sheet metal manufacturer Shape Technology in Addington about 9am on Wednesday.
The chemical caused about half of the staff to suffered watering eyes, sore throats and coughing fits.
St John Ambulance treated about 40 people, and nine were taken to Christchurch Hospital for further attention.
The area in Addington around the metal manufacturing plant was cordoned off, and police went door-to-door in residential streets nearby to advise people to shut their windows and doors.
Inspector Warren Kemp says there was no danger to anyone outside the affected building, and the advisory is only a precaution.
The Fire Service says the gas leak was contained on Wednesday morning and the building ventilated.
