As Tropical Storm Harvey continues to ravage the Gulf Coast of Texas, several major Houston-area oil companies have shut down their facilities as flood waters threaten operations.

Exxon Mobil Corp. (XOM) has closed its refinery in Baytown, Royal Dutch Shell (RDS.A)  announced that it would halt operations at its Deer Park plant and Chevron Phillips Chemical Co., jointly owned by Chevron Corp.  (CVX) and Phillips 66 (PSX) , is shutting its Baytown facility as well.

Shares of Exxon, Shell, Chevron and Phillips 66 were all sinking lower in late-morning trading on Monday. 

Houston-based Phillips 66 has initiated a shutdown of its Sweeny Refinery in Old Ocean. The oil giant also has halted operations at its Pasadena facility. Phillips 66 added that its Houston headquarters are closed through August 28.

Houston-based Enterprise Products Partners LP (EPD) has also shut its Shoup natural gas processing facility, roughly 10 miles west of Corpus Christi. Shares of the midstream services provider were sinking over 1.6% in late-morning trading on Monday. 

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