 In 1939–40 production at Vemork was 20 kilograms, by 1942 production had increased to five kilograms per day.The first attempt to halt the production from the resistance movement was Operation Grouse in October 1942, which failed when the Germans caught the plotters.As a consequence passenger transport after 7 April 1942 from Ingolfsland Station to Rjukan was only permitted for soldiers, police, workers at the plant and schoolchildren.