(CNN) -- Severe storms ripped through parts of the South on Wednesday, cutting a path of destruction from Texas to Tennessee that left at least 12 people dead and hundreds of thousands without power, authorities said.
Even as officials were assessing damage across the region, forecasters said another powerful storm packing high winds and the possibility of tornadoes was bearing down on portions of Mississippi, Alabama, north Georgia and eastern Tennessee.
"The storms are just amazingly explosive and they're covering a very large area," said Greg Carbin with the Weather Service Storm Center in Norman, Oklahoma.
Six people were killed in Alabama after storms moved through overnight and through the morning hours, according to the state Emergency Management Agency. One person was killed in Arkansas, officials in that state said.
Another five people were killed in storm-related incidents in Mississippi, according to the state Emergency Management Agency, which revised its death toll down from six earlier in the day.
Church steeple toppled by storm 
Tornadoes, floods cripple Arkansas "Our thoughts and prayers are with the families who lost loved ones or property in this devastating storm," said Mississippi Gov. Haley Barbour, who declared a state of emergency in 39 of the state's counties. The declaration allows the state to offer aid to the counties during recovery efforts.
Reports of people trapped in homes or overturned vehicles along with reports of downed power lines were coming in from nearly every state in the region, according to emergency management officials.
In Chattanooga, Tennessee, iReporter Erika Dunn said a tree fell on her great-aunt's home. She said her great-aunt reported the storm was so bad she could see a white wall of water coming toward the house. She was headed for her basement and was closing the door of her screened porch when the tree fell.
"It got really strong, really fast," Dunn said.
While no one was hurt in that incident, others across the South were not so lucky.
The state was also bracing for flooding along the Mississippi River,
In northeastern Alabama, there were reports of people trapped in homes in Marshall County after a possible twister touched down earlier in the day, said Lee Rosser, a logistics specialist for the county Emergency Management Agency.
Rescue crews were working to free a number of people trapped at Lake Guntersville State Park, where a number of RVs were parked at the time, said Yasamie August, a spokeswoman for the Alabama Emergency Management Agency.
The storm also damaged an airplane hangar at Birmingham-Shuttlesworth International Airport, airport spokeswoman Toni Bass said. Passenger operations were not affected, she said.
Hundreds of thousands of people across the region were without power, including 269,000 in Birmingham, said Michael Sznajderman, spokesman for Alabama Power.
"We're chipping away" at restoring power, he said, but crews may be forced to halt work as a second line of storms approach.
CNN iReporter Paul Tinsley of Murfreesboro, Tennessee, said he and his wife were awakened overnight by "high winds that were picking up rapidly." He said they grabbed their dogs and ran to a downstairs bathroom. "I was convinced a tornado was seconds away from hitting the house," he said. "Luckily, that wasn't the case."
He said he left the house after the storm passed, and "there are an unbelievable amount of trees down in my neighborhood."
Meanwhile, the National Weather Service issued a tornado watch for portions of southeastern Arkansas, northeastern Louisiana and much of Mississippi until 7 p.m. (8 p.m. ET)
