Computer viruses have infected PCs used at a German nuclear power plant.
The viruses were found on office computers and in a system used to model the movement of nuclear fuel rods.
Power firm RWE said the infection posed no threat to the plant because its control systems were not linked to the internet, so the viruses could not activate.
German federal cyber investigators are now analysing how the Gundremmingen plant became infected.
The viruses were found on the fuel rod modelling system and on 18 USB sticks used as removable data stores on office computers.
Staff found the viruses as they prepared to upgrade the computerised control systems for the plant’s Block B, which is currently not producing power while it undergoes scheduled maintenance.
More than 1,000 computers have now been checked for infection and cleaned up, an RWE spokesman told newspaper Die Zeit. The plant has also improved its security controls.