Extensive renovation work at Third Reich forced labour camp Mauthausen started this morning, it has been reported.Christian Dürr, head of the former concentration camps archive, said today (Weds) that the memorials overall appearance will be improved during the next two years. He added that the installation of a new exhibition was planned as well.Dürr explained some contents of the current exhibit set up in 1970 needed to be updated considering results of research over the past few years.The Nazis imprisoned around 200,000 members of the Jewish community, gypsies, mentally and physically disabled people and political opponents at the camp located in Upper Austria from 1938. Around half of them died before the Allied Troops freed the camp in 1945.The outer wall of the forced labour camp was defaced in February 2009 and earlier this year.Vandals sprayed German-language slogans saying: “The progeny of Muslims are for us what the Jews were to our fathers. Be on your guard. A third world war an eighth crusade”. In the earlier attack last March the walls were defaced with a German sentence saying: “The blood of Turks and Jews is poisonous”.Police are still investigating both incidents.