A tank used for storing animal fat at the Lorneville freezing works caught fire north of Invercargill shortly before midnight.
Five fire engines were sent to the scene at 11.45pm when a tallow tank caught fire at the plant on the northern outskirts of Invercargill.
Fire service spokesman Andrew Norris said the fire was under control by 12.30am.
"We are currently downgrading our attendance there.
"We continue to work with the engineers on site to make sure it is safe."
He said staff were on site as the Alliance-owned freezing works were a 24-hour operation when the fire broke out.
All staff members were accounted for and no one was injured, he said.
It was not yet known what caused the 2000-litre tank to catch fire.
Tallow tanks are used to store fat rendered from beef or mutton, and processed from suet.