Faye Hyde sits on a mattress in what was her yard as she comforts her granddaughter Sierra Goldsmith in Conord Ala. Wednesday. Their home was completely destroyed. (AP) State of emergency in AlabamaTUSCALOOSA, Alabama: Tornadoes and violent storms ripped through seven southern US states, killing at least 284 people in the country's deadliest series of twisters in nearly four decades. The clusters of powerful tornadoes — more than 160 reported in total —combined with storms to cut a swath of destruction heading west to east over several days. In some areas, whole neighborhoods were flattened, cars flipped over and trees and power lines felled, leaving tangled wreckage. Given the apparent scale of the destruction, insurance experts were wary Thursday of estimating damage costs, but believed they would run into the billions of dollars, with the worst impacts concentrated in the Alabama cities of Tuscaloosa and Birmingham. “In terms of the ground-up damage and quite possibly the insured damage, this event will be of historic proportions,” Jose Miranda, an executive with the catastrophe risk modeling firm EQECAT, told Reuters. At least 184 people died in Alabama, the worst-hit state which suffered “massive destruction of property,” Governor Robert Bentley said. The mile (1.6 km)-wide monster twister that tore Wednesday through the town of Tuscaloosa, home to the University of Alabama, may have been the biggest ever to hit the state, said AccuWeather.com meteorologist Josh Nagelberg. Many people told tales of narrow misses. “I made it. I got in a closet, put a pillow over my face and held on for dear life because it started sucking me up,” said Angela Smith of Tuscaloosa, whose neighbor was killed. President Barack Obama said he will visit Alabama Friday to view damage and meet the governor. Obama declared a state of emergency for Alabama and ordered federal aid. In preliminary estimates, other state officials reported 32 killed in Mississippi, 33 in Tennessee, 11 in Arkansas, 14 in Georgia, eight in Virginia and two in Louisiana. Miranda said the estimated costs would be “in the same ballpark” as an Oklahoma City tornado outbreak in 1999 that caused $1.58 billion of damage and a 2003 tornado outbreak in Kansas, Missouri, Arkansas and Oklahoma that caused $4.5 billion of damage. “I would not be surprised to see it in the mid-level billions, singular billions, of dollars,” Miranda said. The Browns Ferry nuclear power plant in Alabama was expected to be shut for days, possibly weeks, as workers repaired damaged transmission lines. But the backup systems worked as intended to prevent a partial meltdown like the nuclear disaster in Japan. “The reactors will remain shut until we have restored the reliability of the transmission system,” said Ray Golden, spokesman for the Tennessee Valley Authority, which owns the 3,274-megawatt plant. Up to 1 million people in Alabama were left without power. Daimler said it had shut down its Mercedes-Benz vehicle assembly plant in Tuscaloosa until Monday because of the tornadoes, but the plant itself sustained only minor damage. Some of the worst devastation occurred in Tuscaloosa, where at least 37 people were killed, including some students. “It sounded like a chain-saw. You could hear the debris hitting things. All I have left is a few clothes and tools that were too heavy for the storm to pick up. It doesn't seem real,” said student Steve Niven, 24. “I can buy new things but you cannot replace the people. I feel sorry for those who lost loved ones,” Niven told Reuters. Shops, shopping malls, drug stores, gas stations and dry cleaners were all flattened in one section of Tuscaloosa, a town of around 95,000 in the west-central part of Alabama.