Soap made from human corpses
During World War I, the British had already accused Germany of using the fat from human bodies to make things.  In April 1917, an important newspaper in London, England called The Times wrote that the Germans were using the bodies of their own dead soldiers to make soap and other products.  It was not until 1925 that the British Foreign Secretary, Sir Austen Chamberlain, officially said that the "corpse factory" story had been an error.