Smelting company Nyrstar has joined the growing list of major companies to suffer losses from South Australia's statewide blackout.
The company says it expects its Port Pirie blast furnace to be out of action for up to 14 days at a cost of more than $5 million.
The company said when the power went out on Wednesday a back-up diesel generator sustained the furnace for several hours.
However, as the power outage continued, the slag in the blast furnace solidified and the furnace could not be tapped.
"We are obviously very disappointed that the power supply in South Australia has failed and the impact that this has caused to the Port Pirie plant," chief executive Bill Scotting said.
"The Port Pirie site is working incredibly hard to ensure we are in a position to restore the blast furnace to full functionality."
Steelmaker Arrium has also halted production at Whyalla as have BHP Billiton and Oz Minerals at their Olympic Dam and Prominent Hill mines.
The Australian Industry Group fears the power outage will lead to big costs.
"The storm damage to power lines has been severe and many individual businesses will have incurred big costs due to the outage occurring in the middle of production processes," Ai Group chief executive Innes Willox said.