Medioimages/Photodisc/Thinkstock(NEW ORLEANS) -- The U.S. Coast Guard reopened on Tuesday a 15-mile section of the Mississippi River, north of New Orleans, that had been closed to prevent damage from flooding.

The portion was closed Sunday night "after reports of sand erosion near flood protection structures were originally thought to have been caused by vessel wakes," the Coast Guard said in a statement.  However, an underground pipe, not river traffic, now appears to be the culprit.

The Coast Guard will closely monitor any new traffic across the reopened section.  Passing will be limited to one vessel at a time, and ships must stay towards the center of the navigation channel, traveling at the slowest and safest speed possible.  Vessels will also be required to check in with the Coast Guard and get its permission before pass through the river.

Copyright 2011 ABC News Radio