HOUSTON - The Mississippi River remained closed in south Louisiana on Thursday, a day after a string of 22 barges broke loose from their tow vessel, the U.S. Coast Guard said. Phillips 66 said operations at the company’s 247,000 barrel per day (bpd) Alliance, Louisiana, refinery, located 18 miles upriver from the closure, had not been impacted by the river closure. The Mississippi is a major artery for the shipment of crude oil, refined products and agricultural products into and out of the United States from the Gulf of Mexico. As of midday Thursday, 21 vessels were waiting to sail down the river to the Gulf and 18 were waiting to move up river, the Coast Guard said. Twenty-one of the barges that broke loose are back under control but one is partially submerged and was being assessed for the risk it may pose to ships attempting to navigate between mile markers 50 and 53 on the river, said Petty Officer Second Class Jonathan Lally, a Coast Guard spokesman. The U.S. Army Corps of Engineers was to assess the navigation risk on Thursday, Lally said. It was unknown when the river would re-open after it was closed on Wednesday. The barges were carrying coal and petroleum coke, which can be used as a coal substitute. No release of the barges’ contents was reported to the Coast Guard, Lally said. Three deep-draft ships were damaged by collisions with a some of the barges. Dry-bulk soybeans from one ship was spilled into the river, but the spill has been secured, he said.