MAYFIELD, Ky. — A desperate search and rescue operation unfolded Saturday across six states mauled the previous evening by rare late-season tornadoes that may have left more than 70 people dead. More than 30 separate tornadoes moved with devastating power and speed through an area stretching from Mississippi in the south to Illinois in the north. As they swept through the region over several hours, the twisters killed dozens, including workers in a candle factory in a flattened Kentucky town, lakeside vacationers in Tennessee and a nursing home resident in Arkansas. While the stream of tornadoes battered dozens of communities, none suffered more than this town of about 10,000 people in southwestern Kentucky, not far from a sweeping bend in the Mississippi River marking the border with Missouri. As the wind stiffened into the high 70 mph range, some employees stuck in the disintegrating Mayfield Consumer Products candle factory took to Facebook to make a video plea for help. "This has been the most devastating tornado event in our state's history," Kentucky Gov. Andy Beshear (D) told reporters Saturday at a late-morning news conference, calling the scale of damage "indescribable." "The level of devastation is unlike anything I've ever seen," he continued. "You see parts of industrial buildings' roofs or sidings in trees, if trees are lucky enough to stand. Huge metal poles bent in half, if not broken. Buildings that are no longer there. Huge trucks that have been picked up and thrown. And sadly, far too many homes that people were likely in, entirely devastated." Following tornado destruction through the Quad State area Beshear spoke with President Biden early Saturday to outline the scope of the damage and the federal assistance necessary to help speed the recovery. Biden later declared a federal emergency for Kentucky, freeing up FEMA assistance and federally subsidized aid, calling the tornado "an unimaginable tragedy." The tornadoes that swept through parts of the Midwest and Tennessee River Valley on Friday night and into early Saturday likely may be recorded as the worst on record in the United States during December. Peak tornado season in the region is usually late spring through early summer. The tornadoes were triggered by a powerful low-pressure system, which lifted from the Southern Great Plains into the Great Lakes. The low-pressure intensified as the polar jet stream, the high-altitude current along which storms track, plunged into the central United States ahead of a blast of record-setting warm air.