Tornadoes across four US Southern states tore through homes, ripped the roof off a shopping mall and blew apart warehouses in a rare spasm of violent winter weather that killed at least 21 people and injured dozens more. The twisters that slammed Arkansas, Mississippi, Tennessee and Kentucky were part of a line of storms that raged across the midsection of the US at the end of a day of Super Tuesday primaries in several states. Candidates including Hillary Rodham Clinton, Barack Obama and Mike Huckabee even paused their victory speeches to remember the victims. A spectacular fire erupted at a natural gas pumping station northeast of Nashville that authorities said could have been damaged by the storms, and an undetermined number of people were reported dead. A couple and their 11-year-old daughter were killed in their home after a tornado touched down near the center of Atkins, a community of 3,000 along the Arkansas River in the central part of the state.