Published: Mar 20, 2011 9:15 PM EDT
Updated: Mar 20, 2011 6:19 PM EDT

NEW ORLEANS (AP) - The U.S. Coast Guard says there is some sort of substance in the water in the Gulf of Mexico, and officials are collecting samples to determine what it is.

Coast Guard spokeswoman Casey Ranel says the agency sent out a cutter Sunday morning to collect samples of the substance, which was spotted off the coast of Louisiana. She says officials are still awaiting the results of testing. Officials also were working to determine how big of an area the substance covered.

The Coast Guard had gotten reports of an oil sheen, but officials have not confirmed the substance is oil. Ranel says dredging had been going on not far away at the mouth of the Mississippi River, and it's possible the substance is silt dredged from the bottom.

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