Rescue crews are using dogs and heat-detecting drones, to search for victims of a tornado that has left 23 people dead in southeast Alabama in the United State.

Lee County Sheriff Jay Jones told a news conference on Monday, that dozens were still missing a day after the giant twister hit the rural Beauregard community, leaving a path of destruction nearly 1.6km wide.

Jones said search crews were basically using everything they could get their hands on, to comb through wreckage and debris.

He said dogs brought in from across Alabama and neighbouring states were used, as well as drones equipped with infrared capability to detect heat signatures.

Jones also said the hardest-hit areas have been checked, but the searches are far from over.