The Coast Guard says a miles-long patch of discolored goop floating in the Gulf of Mexico appears to be caused by river sediment.
The Coast Guard tested the patch Sunday and found only trace amounts of petroleum that were well below the state of Louisiana's standard for clean water. A news release says The Coast Guard believes the discoloration is the result of sediments brought down the Mississippi River.
The investigation began after reports came in Saturday of what appeared to be an oily sheen.
The Coast Guard also said it was investigating separate reports of an oily substance washing up in Grand Isle and other areas nearby. The substance isn't believed to be from last year's massive BP oil spill, but it's being tested.
Cleanup crews and boom are being deployed.