The Coast Guard responded to a fuel spill Thursday at Locks and Dam 27 on the Mississippi River near Granite City.
A vessel passing through the locks and dam was reportedly damaged, rupturing a fuel tank.
The tank holds approximately 20,000 gallons, which is reportedly contained in the lock and dam.
The Mississippi River is closed at Locks and Dam 27 until cleanup operations are complete.
The cause of the incident is under investigation.
According to the U.S. Army Corps of Engineers website, Locks 27 moves more cargo than any other navigation structure on the Mississippi River. The structure is situated near the southern end of the 8.4-mile Chain of Rocks Canal.
To ensure adequate depths in the pool below the old Lock and Dam 26, a low-water dam was constructed across the river, near the old Chain of Rocks bridge. This dam is known as Dam No. 27 and the Chain of Rocks Dam.