Environment Southland staff say they are "concerned" as flood water threatens an old paper mill storing chemicals which could turn toxic when mixed with water.
Thousands of tonnes of a potentially dangerous chemical — known as ouvea premix — are still stored in the former Carter Holt Harvey paper mill in Mataura.
The dross from the New Zealand Aluminium Smelters' (NZAS) Tiwai Point smelter is classified as a class 6 hazardous substance, which can generate poisonous ammonia gas if it comes into contact with water.
![The Mataura River is in full flood through the centre of Gore. Photo / High Country Helicopters](https://www.nzherald.co.nz/resizer/v2/4BJBCUOO3UOQVDXMRCI6PMLN6Q.jpg?auth=06d2fd844f3bf749724515c8e5a1c4e1cf1306b2d007f98dcbda5c4d4376a02d&width=16&height=10&quality=70&smart=true)
Emergency Management Southland said emergency services and others have carried out further flood protection works by sandbagging around the building.