OSLO (Reuters) – Norsk Hydro, one of the world’s largest producers of aluminium, was sustaining a cyber attack on Tuesday that affected its operations, sending its shares lower.

“IT-systems in most business areas are impacted and Hydro is switching to manual operations as far as possible. Hydro is working to contain and neutralize the attack, but does not yet know the full extent of the situation,” it said in a statement.

Norsk Hydro’s website was unavailable on Tuesday. The company was not immediately available for further comment.

Hydro’s shares were down 2.9 percent at 0806 GMT, lagging an Oslo benchmark index up 0.13 percent.