This Jan. 9, 2013 photo shows a subdivision of homes built on the 11.5 mile levee designed to protect Augusta, Ga. from the Savannah River. Inspectors with the U.S. Army Corps of Engineers taking the first-ever inventory of flood control systems overseen by the federal government have found hundreds of structures at risk of failing and endangering people and property in 37 states. (AP Photo/Rainier Ehrhardt)

The Coast Guard says a normally bustling stretch of the Mississippi River remains closed to barge and ship traffic as cleanup crews with booms work to remove an oily sheen near Vicksburg after a barge with 80,000 gallons of oil hit a railroad bridge last weekend.

Coast Guard Lt. Ryan Gomez told The Associated Press on Monday that at least 21 other vessels such as towboats and barges are stalled by the river closing as crews with booms and a skimming device are removing hundreds of gallons of oily water from the river.

He says investigators are trying to determine why a tug pushing two tank barges collided with the bridge early Sunday. Another barge also was damaged.

He says cleanup crews are working to remove the leaking barge's remaining oil.