River oil slick much smaller

NEW ORLEANS, Louisiana (CNN) - The percent of the lower Mississippi River covered by this week's oil spill has been reduced to 20 to 30 percent from an initial 90 percent, Coast Guard Capt. Lincoln Stroh said Friday.

The combination of river bends and swift currents was helping to isolate the oil against the banks, where it is more easily cleaned, he said.

He said four vessels were being allowed to move on the river channel Friday, based on the importance of their cargo. At least two of the vessels were going to and from the Exxon oil refinery in Chalmette, the Coast Guard said.