Emergency officials were counting casualties, picking through rubble and bracing for more carnage Tuesday as a massive, slow-moving but extremely violent storm system refused to release its grip on a wide swath of the nation.

Fourteen people were reported killed Monday after tornadoes roared through Alabama, Mississippi and Tennessee, bringing the preliminary death toll from two days of vicious weather to 31.

The twisters and high winds flattened homes and businesses, uprooted trees and flipped cars across sections of the South and Midwest. The National Weather Service was investigating reports of almost 100 tornadoes. And the destruction may not be over yet.

More than 60 million people from southeastern Michigan to the central Gulf Coast to the Carolinas and southern Virginia are at risk of severe storms and tornadoes Tuesday, AccuWeather meteorologist Alex Sosnowski said.

Mississippi and Alabama remained the states with the highest risk of severe weather, with cities such as Meridian, Miss., and Birmingham, Ala., in the cross hairs for tornadoes, the weather service reported.

The East Coast was not exempt. A forecast of ongoing heavy rain caused the weather service to issue flash flood watches from northern Florida to southern New England.

Mississippi was the hardest hit Monday. At least nine deaths were reported, seven of them in and around Louisville, a town of about 6,600 people. State Sen. Giles Ward said he was huddled in a bathroom with his wife, four other family members and their dog Monday night as a tornado destroyed his two-story brick house and turned his son-in-law's SUV upside down onto the patio in Louisville.

"Our family is OK, thank goodness," Ward told The Clarion-Ledger in Jackson. "Our house as well as all the houses in our neighborhood it appears are destroyed. But our family is safe."

Later, he texted: "I have never prayed so hard in my life. God is good. All we have lost is stuff."

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In Tupelo, Miss., dozens of buildings were damaged and 30 people sought treatment at Northeast Mississippi Medical Center. Four people were admitted.

"It's a very serious situation," Tupelo Mayor Jason Shelton told the Clarion-Ledger. "I am just encouraging everyone to stay inside and be weather aware. There is still a very real danger."

Two deaths were reported in Tennessee. In Lincoln County, the National Weather Service lifted an initial tornado warning shortly after 7 p.m. Monday, but at 8:24 p.m. it warned a tornado was coming. "Catastrophic damage likely with storm in Lincoln County," the message read. "170 (knots) of rotation with debris extending above 20,000 feet."

Within minutes, the warnings grew more dire with winds exceeding 190 mph, The Tennessean reported. Two people were killed in Lincoln County and several homes were destroyed, The Tennessean reports.

The warning seemingly came out of nowhere, said Chris Murdock, who lives 4 miles from a damaged elementary school. Although he and his family didn't see the tornado, the gusts and hail they saw as they went to a friend's basement were enough for him to know this wasn't an average spring storm.

"Just by the looks of it, you could tell something terrible was happening," he said.

In Alabama, University of Alabama student John Servati, a member of the Crimson Tide swim team, was killed when he took shelter in the basement of a Tuscaloosa home and a retaining wall collapsed on him. In Athens, Ala., the Limestone County sheriff's department reported two deaths from a twister that hit a mobile home park west of the town.

Another round of deadly tornadoes tore through the southern U.S. late Monday night, bringing the two-day death toll to more than two dozen people. VPC

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In Arkansas, the death toll from Sunday's tornado stood at 15, 11 of them in Faulkner County, KTHV-TV reported. The tornado has been given a preliminary rating of at least EF3 (136-165 mph winds) by the National Weather Service, one of only two EF3 tornadoes to hit the USA so far this year.

It was the deadliest single tornado in Arkansas in 17 years, the weather service said.

Also Sunday, one person was reported killed in Oklahoma, and emergency officials in Iowa said at least one person was killed by a twister in Keokuk County.

A twister also hit Baxter Springs, Kan., injured at least 25 people and destroying 60 to 70 homes and 20 to 25 businesses in the city of roughly 4,200 residents, according to Cherokee County, Kan., emergency manager Jason Allison.

President Obama has sent his condolences to those affected by tornadoes and promised that the federal government would help in the recovery.

"Your country will be there to help you recover and rebuild as long as it takes," Obama said.

Contributing: William M. Welch, William Cummings; The Associated Press

Clyde Lindley of Brandon, Miss. shoots video of a tornado on Highway 25 in Roxie between Carthage and Louisville during a severe weather outbreak on April 28, 2014.