How did concentration camps stop operating?

When it became obvious to the members of the German High Command that the war was lost, they began to order all prisoners marched out of the camps, and mass-marched in the direction away from the advancing armies. The camp, if ti was a work camp, was then abandoned, or if it was a death camp, it was destroyed, as best as they could. At least, that was the plan. But the Allies from every direction were advancing too fast, and many of the camps - including death camps - were captured intact, with prisoners still there.