Rescuers combed through fields of wreckage after a tornado outbreak roared across the middle of the United States, leaving dozens dead and communities in despair.

A twister carved a track that could rival the longest on record as the storm front smashed apart a candle factory, crushed a nursing home and flattened an Amazon distribution centre.

“I pray that there will be another rescue. I pray that there will be another one or two,” Kentucky Governor Andy Beshear said, as crews sifted through the wreckage of the candle factory in Mayfield, where 110 people were working overnight Friday when the storm hit. Forty of them were rescued.

“We had to, at times, crawl over casualties to get to live victims,” said Jeremy Creason, the city’s fire chief and EMS director.

In Kentucky alone, 22 were confirmed dead by late Saturday, including 11 in and around Bowling Green. But Beshear said upwards of 70 people may have been killed when a twister touched down for more than 200 miles (320 kilometres) in his state and that the number of deaths could eventually exceed 100 across 10 or more counties.

The death toll of 36 across five states includes six people in Illinois, where an Amazon facility was hit; four in Tennessee; two in Arkansas, where a nursing home was destroyed; and two in Missouri.

If early reports are confirmed, the twister “will likely go down perhaps as one of the longest track violent tornadoes in United States history,” said Victor Gensini, a researcher on extreme weather at Northern Illinois University.

The longest tornado on record, in March 1925, tracked for about 220 miles (355 kilometres) through Missouri, Illinois and Indiana. But Gensini said this twister may have touched down for nearly 250 miles (400 kilometres). The storm was all the more remarkable because it came in December when normally colder weather limits tornadoes, he said.

Debris from destroyed buildings and shredded trees covered the ground in Mayfield, a city of about 10,000 in western Kentucky. Twisted metal sheeting, downed power lines and wrecked vehicles lined the streets. Windows and roofs were blown off the buildings that were still standing.