(Bloomberg) -- Exxon Mobil Corp. began shutting units at the fourth-largest refinery in the U.S. as record flooding in Louisiana sent tens of thousands fleeing from their homes.

The Baton Rouge refinery in Louisiana has begun shutting units as the flooding threatened an offsite liquefied petroleum gas storage facility, a person familiar with operations said Wednesday. The plant, located along the Mississippi river, can process 502,500 barrels of crude a day into gasoline, diesel and other fuels.

20,000 people forced from their homes

About 20,000 people have been forced to leave their homes and more than 10,000 are in shelters after nearly 2 feet of rain fell in parts of southern Louisiana, the Associated Press reported Tuesday. Louisiana is home to 18 operable refineries that account for about 18 percent of U.S. capacity, according to Energy Information Administration data.

Through Tuesday, Baton Rouge had received 22.11 inches (56 centimeters) since the start of August, or more than 19 inches above normal, according to the National Weather Service. New Orleans got 7.46 inches or 4.35 inches above normal; Lake Charles had 11.22 inches or 8.69 above normal and Lafayette logged 23.19 or 20.81 higher than the 30-year average.