In 2005 a mass grave from WW II was found at the Stuttgart airport. Hartog Werkendam is possibly among the thirteen Dutch Jews buried here. He was one of the Jewish prisoners at Kommando Echterdingen, near to concentration camp Natzweiler, who was set to work on the airport of Stuttgart late 1944. The remains have been properly reburied.
News letter of the War Graves Foundation 2005 (in Dutch)