Aerial photographs of a North Carolina farm have highlighted growing concerns about pig waste stored in ponds.
Floodwaters continue to rise after Hurricane Florence, and authorities are closely monitoring any potential leaks from what are called pig waste lagoons.
The state's Department of Environmental Quality released data on Tuesday saying at least 13 lagoons have overflowed and 64 more are at risk.
Environmental groups have warned people not to swim in the waste.
North Carolina's Department of Environmental Quality has an updating dashboard on its website recording known issues with the 3,300 lagoons in the state.
As the New York Times reports, the agency depends on farmers self-reporting incidents of overflowing lagoons - and since many have left their farms to escape the floodwaters, the number could well be higher.
However, the North Carolina Pork Council - the organisation for pork producers in the state - says there are fewer overflowing lagoons than the Department of Environmental Quality is reporting.
North Carolina has more than nine million pigs, many which live in the hurricane-devastated counties of Sampson and Duplin, south-east of state capital Raleigh.
Pig waste on the farms is run off into the lagoons and then mixed with water and anaerobic bacteria to treat the excrement.
This bacteria is what gives the pools their pinkish hue.
There are growing fears that leaks from these pools could cause an environmental catastrophe - with waste polluting rivers, lakes and groundwater, and causing numerous medical problems.
After Hurricane Floyd hit the state in 1999, pig waste drowned animals and caused mass fish deaths.
Residents who live near the pig farms have often complained about their effect on lives and wellbeing.
Local media reported on recent attempts to curtail nuisance laws in North Carolina allowing neighbours to sue pig farmers.
"Our laws must balance the needs of businesses versus property rights," state governor Roy Cooper reportedly said.
"Giving one industry special treatment at the expense of its neighbours is unfair."
A recently published Duke University study suggested pig farms in the state could be an influence in poor health and low life expectancy for neighbouring residents, although the research stated it could be one of many factors and is not an explicit cause.