Beginning in September 1944, a group of Jewish prisoners, presumably brought from outside the Wartheland District, was forced to exhume and cremate any remaining corpses from the mass graves at Chełmno as part of Operation 1005 and to obliterate any other evidence of mass murder operations. The SS and police shot about half of the 80-man detachment after this work was done in November 1944. The Germans abandoned the Chełmno killing center on January 17, 1945, as the Soviet army approached. The SS killed at least 152,000 people at Chełmno between December 1941 and March 1943 and in June/July 1944. (Note: a 1946-47 report places the number closer to 340,000).