NORMAN, Okla. — A line of severe thunderstorms roared out of Texas and across the South on Monday, killing four people in a home in Alabama while spawning flash flooding, power failures, and destructive winds to numerous other areas.

Kris Ware, a spokeswoman for the Dothan Houston County Emergency Management Agency, said four people were killed when a tree fell on their mobile home in Rehobeth.

Damage was recorded in at least 28 Mississippi counties, 15 Louisiana parishes, and 15 Texas counties.

More than 50,000 customers in Louisiana and more than 30,000 in Mississippi lost power at the height of the storm, according to utilities.

The squall line hit Louisiana’s Avoyelles Parish just before noon. Bunkie Fire Chief Joey Frank said trees fell on three houses in his town, while Marksville Fire Chief Jerry Bordelon said a fireworks stand in the Walmart parking lot was tossed 30 or 40 yards and mangled. The storm also knocked over 18-wheel truck trailers and punched holes in the Walmart’s roof.

The fire department ordered shoppers to leave the store, but some didn’t want to leave even as managers closed it. ‘‘Believe it or not, we had some people in there who were still trying to shop,’’ Bordelon said.

Storms in central Mississippi near Mendenhall and Mount Olive were preliminarily identified as tornadoes by the National Weather Service.