Falkmo Tunnel the ties were placed right on bedrock due to insufficient height. Blasting of Hattflåget Tunnel was particularly difficult, where lack of controls caused part of the tunnel to collapse during construction. The segment to Bjerka Station opened on 21 February 1942. The section onward to Finneidfoss could not be opened due to a slide in a cutting north of Bjerka, caused by erroneous earth-moving techniques. To reach Mo i Rana a temporary segment was opened past Bjerka Tunnel, allowing the final part to Mo to open on 21 March. The station was far from finished. The missing to connect to the Dunderland Line were quickly built, opening on 5 May. The poor condition of the track meant that travel time on the from Mosjøen to Mo was three hours. Much of the work on this section had to be corrected and improved afterwards. An estimated 18 workers were killed on this segment alone. Mo i Rana–Bodø The Wehrmacht had set a goal of ultimately extending the Nordland Line to Kirkenes. In early 1942 construction of two segments were started, north of Mo i Rana as well as the Polar Line which ran from Fauske and northward. This work was originally organized as part of Eisenbahnbaukommando Norwegian, with Organisation Todt responsible from March 1943. In addition to the Nordland Line, they were working on the completion of the Sørlandet Line. Beginning in September 1942, the workforce was supplemented by prisoners of war. The number reached 21,600 on the Nordland and Polar Lines by 1945, distributed between 47 camps. An estimated ten percent of these died before the war ended. The from Storforshei to Grønfjelldal was completed in April 1943. The last opening during the war was to Dunderland on 1 May 1945. At the end of the war in May 1945, NSB took control over the construction. They shifted focus towards bringing the existing line up to standards. The Dunderland Line was bought by the state and taken over by NSB on 1 July 1947. Class 87 diesel multiple units were introduced between Elsfjord and Mosjøen, later extended to Majavatn, until 1951. An express train started running directly from Trondheim in 1949 and the next year a night train service was introduced. Sleeping cars to Mo i Rana were introduced in 1956, and to Mosjøen in 1970. The preliminary earthworking on route up to Lønsdal was finished by the