(Reuters) - The Mississippi River was closed to traffic at two locations on Thursday as barge tows ran aground near Greenville, Arkansas, and La Crosse, Wisconsin, due to low water amid the worst U.S. drought in 56 years, private and government sources said.
It was unclear when the key shipping waterway might be reopened to commercial traffic, they said.
Low water has restricted barge drafts to a lighter-than-normal nine feet and limited barge tows to fewer barges on numerous sections of the Mississippi River.
But even as vessels have lightened their cargo loads, numerous boats have run aground in recent weeks, forcing temporary river closures and snarling north- and southbound freight traffic. The river is a major shipping lane for grains, oilseeds, fertilizer, salt, coal, and other cargo.
The Bootsie B towboat was pushing 13 empty barges and 15 barges loaded with fertilizer and salt when they ran aground at mile marker 525 near Greenville, said Petty Officer Ryan Tippets of the U.S. Coast Guard's 8th district external affairs division.
The vessels have been refloated and there were no reports of injuries or pollution, he said.
Another vessel ran aground on Thursday near La Crosse, Wisconsin, due to low water, forcing a temporary closure of the river, but other details were not immediately available, a shipping industry source said.
(Reporting by Karl Plume in Chicago; Editing by Bob Burgdorfer)