The operator of one of the largest aluminium plants in Europe has switched to manual operations at its smelting facilities following a cyber-attack due to automatic Computerized system.
Hydro, which employs more than 35,000 people across 40 countries, says the attack began on Monday evening and is still under way.
A spokesman told the BBC that he could not yet confirm what type of cyber-attack the firm was facing.
The company's website is currently down and it is posting updates to Facebook.
Hydro said machinery at its Norwegian smelting plants had digital systems to ensure their efficiency, but they had to be turned off.
"They are much more reliant today on computerized systems than they were some years ago," a spokesman said.
"But they have the option of reverting back to methods that are not as computerized, so we are able to continue production."
