Almost 250 people have died after the south eastern US was pummelled by scores of tornadoes.
Search-and-rescue teams were last night hunting for survivors beneath fallen masonry and tangled joists, power lines and fallen trees in towns and hamlets across seven states — ravaged by the worst outbreak of tornadoes seen in almost four decades.
Stunned residents of Tuscaloosa in Alabama awoke yesterday to discover a city partly razed by a killer twister that cut a swath more than a mile wide and may have come close to an F5 level, the highest on the intensity scale.
Shopping centres and whole residential neighbourhoods were shredded, reduced to a jumble of destruction.
At least 169 people died in Alabama alone.
Tornado swarms are not uncommon across the central belt of the US in the spring, when cold air battles with much warmer, humid air pushing up from the Gulf of Mexico.
But not since 1974, when a single outbreak killed 315 people, has twister activity been as high as this year.
The death toll from Wednesday's super-outbreak, which saw tornado touchdowns along a corridor from Texas to Virginia, stood at 249 and officials said it was likely to rise further as new victims were dug from destroyed homes and businesses.
Avalanche rescue dogs were deployed in some areas to seek out victims.
Among the affected states, the worst of the damage appeared to be in Alabama.
Those killed in Tuscaloosa, home to the University of Alabama, stood at |15 while hundreds of others suffered |injuries.
Meanwhile, a nuclear power plant at Browns Ferry, to the west of Huntsville, was knocked off-line with safety power coming only from back-up generators.
Power officials said it might be weeks before the plant is back on-line.
This tornado season may be one of the deadliest ever, even though modern forecasting and communications technology, including social sites such as Twitter and Facebook, have made it easier to issue general warnings than was the case a few years ago.
But storms like the ones that raked through the region on Wednesday can sometimes be too fierce, gouging everything they touch, no matter how prepared people are.
An F5-force tornado will destroy a brick building down to its foundations, while felling trees and lifting vehicles clean off the road before dumping them elsewhere. In those conditions, there is nowhere for people to hide if they are in its path.