(Bloomberg) -- Exxon MobilCorp. began shutting units at the fourth-largest refinery inthe U.S. as record flooding in Louisiana sent tens of thousandsfleeing from their homes.

The Baton Rouge refinery in Louisiana has begun shutting unitsas the flooding threatened an offsite liquefied petroleum gasstorage facility, a person familiar with operations said Wednesday.The plant, located along the Mississippi river, can process 502,500barrels 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 morethan 10,000 are in shelters after nearly 2 feet of rain fell inparts of southern Louisiana, the Associated Press reported Tuesday.Louisiana is home to 18 operable refineries that account for about18 percent of U.S. capacity, according to Energy Information Administration data.

Through Tuesday, Baton Rouge had received 22.11 inches (56centimeters) since the start of August, or more than 19 inchesabove normal, according to the National Weather Service. NewOrleans got 7.46 inches or 4.35 inches above normal; Lake Charleshad 11.22 inches or 8.69 above normal and Lafayette logged 23.19 or20.81 higher than the 30-year average.

Related: Historic Louisiana flooding leaves at least 11dead; 20,000 rescued [photos]

Governor John Bel Edwards declared an emergency on Friday.Residents in 20 parishes are eligible for federal assistance and intwo days 39,000 people have registered, the Governor’s Office ofHomeland Security and Emergency Preparedness said.

Motiva Enterprises LLC said yesterday in an online messageto employees that it will staff the Convent refinery with onlyessential personnel through Wednesday because of flooding and roadclosings.

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