Norwegian aluminum giant Norsk Hydro has suffered a severe cyberattack forcing the company to switch to manual production, while some production plants in Europe and the US had to shut down altogether.

A statement by the company said that “IT systems in most business areas are impacted and Hydro is switching to manual operations as far as possible.” The firm also said it was “working to contain and neutralize the attack,” admitting that it did “not yet know the full extent of the situation.” It was not immediately clear what kind of attack has hit the company, but the problems seem to have started last night.

Read more: Aluminium Giant Norsk Hydro Suffers Major Cyber-Attack