An all-clear has been given and workers allowed back after a chlorine leak at the Carter Holt pulp and paper plant at Kinleith, just south of Tokoroa.
Emergency services were called to the scene just after 11am on Wednesday.
The Fire Service says an emergency valve released the gas and the plant had to be evacuated.
It says a cloud of chlorine gas was dispersed by a north-westerly wind that took it over forestry land and not the town.
