The operator of one of the largest aluminium plants in Europe has switched to manual operations at its smelting facilities following a cyber-attack.
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.
"IT systems in most business areas are impacted," the firm said.
Hydro told the BBC that digital systems at its Norwegian smelting plants were programmed to ensure machinery worked efficiently.
However, these systems had had to be turned off.
"They are much more reliant today on computerised systems than they were some years ago," a spokesman said.
"But they have the option of reverting back to methods that are not as computerised, so we are able to continue production."
The firm said it was working to contain and "neutralise" the attack.
More to follow