LONGVIEW, Wash. — A massive chemical tank holding nearly a million gallons of a highly corrosive liquid imploded and collapsed Tuesday at a Washington paper mill, killing at least one worker and leaving nine others unaccounted for with no hope for rescue, authorities said. Another nine people were injured, some severely, in the spill at Nippon Dynawave Packaging Co. in Longview. The cause remained unclear. “At the moment we are not aware of any rescues that are yet to be made,” Cowlitz Fire and Rescue Chief Scott Goldstein said during a Tuesday evening news conference in which officials repeatedly referred to the situation as a recovery effort. That effort would not resume until Wednesday morning, when emergency responders planned to work on stabilizing the collapsed tank, which still had about 90,000 gallons (more than 340,000 liters) of a chemical brew known as “white liquor” inside, and then search for the missing, Goldstein said.