(Portland, OR) -- Demolition of the Centennial Mills building in Portland went fast on Tuesday. The metal water tower on top of the building was dropped inside of the structure with explosives on Monday. Crews started pulling the walls into the interior of the building and progress went fast. The contractor has been taking steps to minimize dust and runoff, because of potential asbestos pollution. Once the unstable hazards have been removed, investigators will search for clues to the cause of the fire and conduct a forensic examination. K-9s indicated there might be human remains in the burned-out building.