NEW ORLEANS - The Coast Guard has reopened the Upper Mississippi River to marine traffic at 11:45 a.m. today.A portion of the river was closed due to a sunken towing vessel located at mile marker 173, earlier today. The closure took place when the Charlie Boy, a previously missing 61-foot towing vessel, was located by the U.S. Army Corps of engineers outside of the navigable channel on the Upper Mississippi River at approximately 11:30 a.m., today.Salvage operations are pending.The Coast Guard is investigating the cause of the incident.