Around 2 million people across the South braced for more devastating flooding and hail on Monday after days of relentless rain and violent thunderstorms left six dead and triggered evacuations.
Flash-flood warnings were issued in Louisiana, Missouri and Tennessee overnight and into the morning, according to the National Weather Service.
Parts of Kentucky, Tennessee, Arkansas, Mississippi, Alabama, Louisiana and Texas were also under flood or river warnings as of around 5 a.m. on Monday, Weather Channel meteorologist Kevin Roth said.
Some 12 tornadoes or possible tornadoes were reported in Arkansas Sunday and overnight, Roth added. No injuries or deaths were reported.
The ongoing storm was aggravating flooding in major rivers, especially along the Louisiana-Texas border, with some 3,300 residents having been evacuated in Louisiana alone, The Associated Press reported. President Barack Obama signed an order declaring the flooding in Louisiana a major disaster on Sunday.
Emergency management officials in Springfield, Missouri — some 220 miles southwest of Saint Louis — told residents late Sunday to stay home and avoid driving through dangerous flood conditions in surrounding Greene County.
"We are really under a flash-flood emergency. Those roadways that are typically not impacted are being impacted today," Chet Hunter of the Springfield-Greene County Office of Emergency Management said in a video posted on department's Facebook's page. "We have significant amounts of road closures that are not normally closed. So our caution to you would be to not travel this evening. If there is not a need to travel then stay home."
Emergency responders had conducted more than 60 water rescues by around 11 p.m. Sunday (midnight ET), the department announced. Flood warnings would remain in effect until 7 a.m. (8 a.m. ET).
Roth advised residents of flash-flood-hit regions to delay their commutes if possible.
"Certainly don't cross any area of water, no matter how small it looks — that's were a lot of people get into trouble," he added.
On Sunday, emergency responders in Hattiesburg, Mississippi, warned that the rising flood waters could bring toxins with them.
"If you can look at all the trash and all that's floating through the houses, gasoline … there's all sorts of different toxins. I mean, that's floating through all these people's houses," Glen Moore, of Hattiesburg Mississippi's emergency management office told NBC News.
The flooding has already proved deadly. A 78-year-old man drowned Saturday night near Clarence, Louisiana, while trying to get to his home in an aluminum boat to retrieve personal items, the Natchitoches Parish Sheriff's Office said.
Two other people in the boat were safely rescued, but the incident brought the death toll from the storms to at least six. Three other people were previously known to have died in Louisiana, along with one each in Texas and Oklahoma.