Aerial photographs show widespread devastation to farms and industrial sites in eastern North Carolina.
But conditions remain so bad on the ground that inspectors have been prevented from visiting some of the hardest hit areas to collect samples of the floodwater for lab testing.
Photographs have revealed tell-tale trails of rainbow-colored sheen indicating potential contamination visible on top of the black floodwaters.
State officials say about 3.4 million chickens and turkeys and 5,500 hogs have been killed in flooding from Florence as rising North Carolina rivers swamped dozens of farm buildings where the animals were being raised for market.