An unidentified oily substance had coated the Potomac River for at least eight miles as of Friday and left birds covered in the fluid.
The oily sheen could be seen Friday at Roaches Run Waterfowl Sanctuary, just north of Ronald Reagan Washington National Airport. The Coast Guard used a helicopter to survey how far the substance had traveled and spotted it as far down the river as Mount Vernon, Virginia. It was first spotted Feb. 1.
About 20 geese and several ducks were found Friday coated in oil, a Potomac Riverkeeper Network employee said. Fish were found dead.
The substance also was found on birds in D.C., near the National Mall.
Floating barriers have been placed in the water to stop the spill from spreading.
Dominion Virginia Power said a spill of mineral oil occurred Jan. 24 at a transformer station near Roaches Run. But Lt. David Ruhlig of the Coast Guard said that may be unrelated.
"We haven't linked those two together," he said. "We haven't ruled any source out at this point."
The oily substance has no impact on drinking water in the area, officials said. Additional tests will be conducted in the following days.
If you see a bird in need of help, call 311.