The fire at the Winston Weaver fertilizer plant has raised concerns that nearby waterways may have become contaminated.
State and Forsyth County health officials are investigating the runoff caused by the firefighting and recent rainwater.
In the meantime, they've issued a recreational water advisory for parts of three waterways likely to carry the runoff. Monarcas Creek, just west of the fertilizer plant, is likely the most affected.
The downstream waterways of Mill Creek and Muddy Creek to the Muddy Creek Wastewater Treatment Plant in southwestern Forsyth County are also included in the advisory.
Public health officials are urging people to stay away from the water until test results come in. They say residents may notice fish kills or sheen on the water.
If you're concerned about exposure for you, your family, or your pets, contact your health care provider or veterinarian.