(Adds background, details)
March 14 (Reuters) - The U.S. Coast Guard closed the Mississippi River to all vessel traffic on Thursday near Baton Rouge, Louisiana, after a towboat sank in the major commodity shipping waterway.
The river was closed from mile marker 224.5 to 226 while a Coast Guard team monitors the water for any signs of pollution and an Army Corps of Engineers crew searches for the sunken towboat.
Four crew members aboard the vessel Michelle Ann were rescued with no reported injuries, the Coast Guard said. Officials are investigating the cause of the sinking.
The Coast Guard declined to project how long the river would remain closed, according to a spokesman.
Heavy rains and snow melt have swelled the Mississippi River and its tributaries, which are major shipping channels for moving bulk imports and exports of commodities including grains, metals and coal.
Some 60 percent of all U.S. grain exports exit the country via Gulf Coast export terminals that are primarily supplied by barge loads of grain from Midwest farms.
Commercial shipping on large sections of the river system has been restricted in recent weeks due to flooding and strong currents. The lower Mississippi River has been closed at least twice in the past month for barge breakaway incidents, which typically occur during periods of high water. (Reporting by Karl Plume in Chicago; Editing by Sandra Maler and Marguerita Choy)