The original native inhabitants were not allowed to return to Narva after the war, and immigrant Russian-speaking workers from other parts of the USSR were brought in to populate the city. The main reason behind this was a plan to build a secret uranium processing plant in the city, which would turn Narva into a closed town. In 1947 nearby Sillamäe was selected as the location of the factory instead of Narva, but the existence of such a plan was decisive for the development of Narva in the postwar years, and thus also shaped its later evolution. The planned uranium factory and other large-scale industrial developments, like the restoring of Kreenholm Manufacture, were the driving force behind the influx of internal migrants from other parts of the Soviet Union, mainly Russia.