Clear-up after tornadoes wreak havoc across US Midwest

US authorities in several Midwestern states are searching for survivors and clearing damage after a string of powerful storms and tornadoes left at least 37 people dead.

The states of Indiana, Kentucky, Ohio, Georgia and Alabama were all hit by the intense winds which flattened homes, lifted rooftops and downed powerlines.

An unknown number of people are missing after communication lines were damaged.

A total of 90 tornadoes and 700 severe weather events were reported on Friday.

Ohio Governor John Kasich has declared a state of emergency, the Associated Press reports.

President Barack Obama has offered federal government help to the affected states.

Correspondents say it will be impossible to make an immediate assessment of the full extent of the damage.

Tornadoes occur all year round in the US, although the strength of this week's storms was unusual for the time of year - the peak period is March to May in the southern US and later further north.

'Completely gone'

At least 18 people died in Kentucky, reports said, and another 14 in neighbouring Indiana.

The small town of Marysville, Indiana, was almost completely destroyed, with the town's water tower one of the few buildings to remain undamaged, local reports said.

Clark County Sheriff Danny Rodden said that residents had been warned of oncoming storms but added: "This was the worst-case scenario. There's no way you can prepare for something like this."

In the town of Henryville, a roof was ripped from a school and a school bus thrown against a restaurant. No-one was seriously injured in either incident.

"We're not unfamiliar with Mother Nature's wrath out here in Indiana," Governor Mitch Daniels told CNN during a visit to the stricken south-eastern corner of the state on Saturday.

"But this is about as serious as we've seen in the years since I've been in this job," he said as he viewed the damage in Henryville.

Prison damaged

A toddler was in a critical condition in hospital in Kentucky after being found alive and alone in a field near the town of Salem, southern Indiana.

In nearby Chelsea, three members of one family - including a four-year-old child - died in their house when the storm struck.

The child and mother were huddled in a basement when the storm hit and sucked the child from her arms. The mother survived, but her 70-year-old grandparents, who were upstairs, both died.

"She was in the cellar with the boy when the tornado hit. It blew him right out of her hands," Tony Williams, the owner of the town's General Store said.

"They found the bodies in the field outside," he added, referring to the grandparents.

Three people were reported dead in Ohio while in northern Alabama, one person died.

At least 40 homes were destroyed and 150 damaged in the state while the roof of a prison in the path of the storm was damaged, forcing 300 inmates to be moved to another part of the facility.

Earlier this week, 13 people died after twisters swept through Missouri, Kansas, Illinois and Tennessee.

The US National Weather Service had described the situation as particularly dangerous - the mild winter has created conditions where cold fronts collide with warmer air causing the tornados to form.

Last year they killed more than 500 people making it the third deadliest year on record.