The river border was closely watched for escapees, many of whom drowned attempting to cross.[75] Numerous bridges blown up in the closing days of the Second World War remained in ruins, while other surviving bridges were blocked or demolished on the East German side.[76] There were no ferry crossings and river barges were rigorously inspected by the GDR border guards.[77] To prevent escape attempts, the East German river banks were barricaded with a continuous line of metal fences and concrete walls.