Authorities have accounted for dozens of people who were previously listed as missing after the weekend’s deadly flooding in the US state of Tennessee, where the full scope of damage is coming into view.

Officials have also lowered the number of those killed by the storm – which destroyed homes and businesses, swept cars off the road, and left streets awash in mud – dropping the estimate to 18 from 21.

The death toll includes infant twins, who were swept from their father’s arms in the torrent.

As residents have got in touch with authorities, or found family members and friends at the local reunification centre, only three people remain missing. Earlier, officials had put the number of missing at 50.

The scope of the damage came into sharper focus in hardest-hit Humphreys County, as rescue teams continue to search house-to-house with trained dogs looking for victims.

“We’ve got 100 to 125 homes off the foundation, twisted and some that are gone. And that’s just the ones we’ve seen,” Humphreys County Sheriff Chris Davis said on Tuesday (local time).

Hundreds of other homes were water-damaged and uninhabitable, officials said.

US President Joe Biden declared a major disaster in the state of Tennessee and ordered federal aid.

-AAP