Low water has exposed a bed of &#8220mystery rocks” along the east bank of the Mississippi River near Riverfront Park.

A U.S. Army Corps of Engineers official said he could not positively identify what appears to be a manmade stabilizing structure.

&#8220Nobody knows what it is,” said Frank Worley, deputy public affairs officer for the Vicksburg District. &#8220We can’t even say it was part of something we once did. It could be something that got moved down the river.”

The 68,000-square-mile Vicksburg District encompasses seven river basins, including 278 miles of the Mississippi River’s main stem, in Arkansas, Louisiana and Mississippi. The district is also responsible for about 800 miles of commercially navigable streams and rivers. Revetments and jetties and other structures are put in place to guide the rivers and help keep channels open.

It is rare for the rocks that extend toward midriver to be seen.

&#8220We’re low – below average for certain,” said Robert Simrall, chief of the Water Control Management office. &#8220We were at 2.3 feet today and earlier this weekend we were at 0.1.”

Normal readings for this time of year are 7 or 8 feet on the gauge – which is a measure of relative stages, not the river’s depth.

A rise is forecast to 3.9 feet by Saturday, meaning the rocks will slip back below the muddy flow and not be seen again for years.

Worley said it is unusual for the river’s east bank at Vicksburg to be as visible as it was Wednesday.

&#8220That area is a good 20-30-foot drop below the park,” he said. &#8220Normally, that sandy area is not exposed. We’re talking an old, old structure.”

Worley did acknowledge the structure could be what is called rip-rap, or broken stone used for riverbank revetments.

&#8220It might be an old part of a revetment that’s moved down the river, or it could just be a natural part of the river.”

In the first half of the last century, the area where the park is located was an industrial site. There’s a chance the rocks were placed by private interests.

Today, no one may build structures extending into commercial waterways without a study and a Corps permit.