NEW ORLEANS — The U.S. Coast Guard says workers are using boom to contain a 17-mile-long sheen on the Mississippi River near Fort Adams in Wilkinson County, Miss., The Associated Press reported Thursday.

No environmental damage has been reported and the river remained open to shipping on Thursday.

Wilkinson County is in southwest Mississippi, about 40 miles south of Natchez.

The Coast Guard says the substance — spotted by a Coast Guard patrol on Wednesday — is believed to be a petroleum-based product.

Details on the quantity of substance in the water were not available. However, the Coast Guard identified the responsible party as El Toro Production Co. of Natchez, Miss.

The Coast Guard says two companies have been hired to assess and respond to the spill.