A two-year-old girl who was found barely alive amid the bodies of her parents and siblings after horrific tornadoes hit the United States, died Sunday after a 48-hour fight for life.

Angel Babcock was discovered in a field near her family's home in New Pekin, southern Indiana after Friday's horrific weather and was taken to hospital in neighboring Kentucky where her condition was initially described as critical.

The two-year-old, who becomes the 37th victim of devastating weather that pummeled the country on Friday, had lost her parents, two-month old sister, and three-year-old brother in the storms.

Relatives from her extended family, however, chose to turn off the toddler's life support system on Sunday afternoon, Kentucky Coroner Bob Jones told CNN.

Emergency officials in Indiana confirmed the child's death and said she was the state's 13th fatality, revising down an earlier higher toll of 14.

Indiana Governor Mitch Daniels earlier commended action taken before the storms as well as subsequent efforts to support those affected.

"I think we were as ready as possible... and the reaction afterward was the fastest we've ever done," Daniels told CBS television.

"With all of that, when Mother Nature decides to work her wrath on we mere mortals you remember how inadequate the best of human action can be," he said.

Deaths from the tornadoes have been reported in Kentucky, Indiana, Ohio, Alabama, and in Georgia.

Despite the toll and damage from the bad weather, the US Federal Emergency Management Agency (FEMA) said on Sunday that it had received no requests for assistance from the states hit by the deadly storms.

While tornado watches were discontinued on Sunday, the National Weather Service (NWS) forecast a cold front moving through some affected regions.

Temperatures were expected to fall below freezing by Sunday night and a mix of rain and snow was to become all snow, the service warned, a development that could pose further problems for people left without homes.