Fire and explosions at a hazardous waste plant in Apex, North Carolina, forced the evacuation of about 16,000 people:
People "are putting themselves in very grave danger by being near or around this smoke. If you see smoke, get away from it." said Bruce Radford, manager of the Raleigh suburban town.
"There are pesticides, oxides, chlorine gases, there are all grades of contaminated material in this fire and in this smoke," he said.
They can't even fight the fire, for fear of toxic runoff:
Although flames reached 150 feet, officials are letting the fire burn itself out to avoid toxic runoff and the threat to firefighters.
"Water would flood the area with toxic chemicals," Radford said. "It just needs to burn up."