A top official monitoring the Gulf oil spill says there is no evidence that oil is accumulating on the sea floor in the Gulf of Mexico.

NOAA Administrator Jane Lubchenco says oil from the massive BP spill that never made it to the surface of the Gulf has been dispersed naturally or chemically.

Lubchenco spoke as a new government report released Wednesday said that only about a quarter of the spilled oil remains in the Gulf, with the rest having been contained, cleaned up or having disappeared.