Tornadoes raked America’s southern Plains region, overturning cars on an Oklahoma City motorway and destroying dozens of homes.

The US region hit by a deadly tornado less than two weeks ago is being slammed again. The Oklahoma Highway Patrol says a mother and baby were killed, and emergency officials said reports of injuries were “widespread”.

A deadly winter storm that caked America’s centre with a thick layer of ice claimed at least 17 lives and blacked out more than 600,000 homes and businesses.

United States and Argentine authorities were investigating how a stick of dynamite in a college student’s checked luggage ended up on a Houston-bound flight, one of seven security incidents that disrupted US flights in a day.