Federal environmental officials say Duke Energy has completed removal of large pockets of coal ash from the Dan River following a massive spill at a North Carolina power plant.

The U.S. Environmental Protection Agency's on-scene coordinator, Myles Bartos, said Thursday that Duke had dredged up about 2,500 tons of ash and contaminated sediment, as well as another 500 tons that had accumulated in settling tanks at downstream municipal water treatment plants in Virginia. Coal ash contains toxic heavy metals such as arsenic, mercury and selenium.

Duke estimates about 39,000 tons of coal ash spewed into the Dan after a drainage pipe collapsed Feb. 2, turning the river gray for more than 70 miles. Bartos says the clean-up is considered complete, though Duke has recovered only a fraction of the total spilled.