BELLE CHASSE, La., April 13 (UPI) -- The U.S. Coast Guard said it was investigating what caused 18,000 gallons of crude oil to spill into the Delta National Wildlife Refuge in Louisiana.
Crude oil from Chevron pipeline spilled into a canal April 6, contaminating roughly 160 square miles.
The Coast Guard said it was making "steady progress" on cleanup operations as workers, boats and equipment descend on the area.
The Delta National Wildlife Refuge covers around 49,000 acres of marshland along the southeast coast of Louisiana. The area is an important habitat for migrating bird species.
The Coast Guard said it took measures to keep wildlife out of the contaminated area. Bird deterrent devices were deployed to keep birds away.
"Observed impact to wildlife has been minimal," the Coast Guard said in a statement.
Contractors dredging part of the area for Exxon Mobil noticed the leak. The Coast Guard said it was investigating the cause of the accident.
