A fire in a building in Gore forced the evacuation of nearby properties and took some 90 firefighters to extinguish.
Emergency services were alerted to the fire at Livestock Supplies on Sunday evening.
The police evacuated nearby supermarkets, a church and a pub, because of concerns about smoke.
Fire Service Area Commander Bruce Stubbs said crews contained the fire on Sunday evening and remained at the scene. The fire is now completely out.
Three firefighters were treated for smoke inhalation and two diggers were brought in to pull down the unstable external walls of the building that posed a threat to neighbouring properties.
Toxic chemicals are known to be inside the building and the Southland Regional Council has staff at the scene to work out if there are any dangers to the environment.
Fire investigators are also at the scene. There has been no immedate indication of how the fire started.