Floodwaters breached a dam near a Duke Energy power plant on Friday, the company said, raising fears that toxic coal ash could reach the nearby Cape Fear River.

The rising waters also swamped a 625-megawatt natural gas plant near the site, forcing it to shut down, the company said.

Fears about the situation at Duke’s L.V. Sutton power plant near Wilmington have been growing since before Hurricane Florence made landfall. The storm poured down so much rain that the wall of a coal ash landfill near the former coal plant, which sits along the banks of Sutton Lake and near the Cape Fear River, failed in several places. A special black membrane installed to contain the waste was torn open in at least two spots.

Duke estimated that the storm had washed away more than 2,000 cubic yards of coal waste — enough to fill more than 150 dump trucks.

On Friday came more bad news. The company said the dam separating the Cape Fear River from man-made Sutton Lake, which holds water used to cool discharges from the power plant, suffered one large breach and several smaller ones.

Meanwhile, a steel wall separating the oldest of four coal ash disposal basins at the site was submerged by floodwater, leaving only a small earthen berm to prevent waste from reaching the lake and potentially the Cape Fear River.

“We cannot rule out that coal ash is moving into the river,” Duke spokeswoman Paige Sheehan said in an email.