Updated at 3:45 p.m. ET
The U.S. Coast Guard has shut down a section of the Mississippi River south of Paducah, Ky., after two tow boats collided, causing an oil spill of unknown size.
In a statement, the Coast Guard said that the collision occurred Wednesday at 8:22 p.m. at Mile Marker 937, just north of Columbus, Ky.
"The collision caused damage to at least one barge containing clarified slurry oil, rupturing the cargo tank and discharging an unknown amount of oil into the Mississippi River," the statement said.
The barge was carrying about 1 million gallons of the clarified slurry, according to the Coast Guard, which says it believes the spill involves a maximum of 250,000 gallons.
The statement says that with the exception of vessels authorized to be working on the incident, river traffic has been halted between Mile Marker 938 and Mile Marker 922, south of Hickman.
The Associated Press adds:
"The Coast Guard said it was working with the barge owner, Inland Marine Services, and an oil spill response organization to determine the exact amount of oil that poured into the water.
"It wasn't known how long the river would be closed. The tow boats were moored on opposite sides of the river and a long gash was apparent in the smaller vessel. River traffic was backed up on both sides."