Nearly 100 tornadoes raked across the central United States, leaving five people dead and at least 29 injured yesterday in Oklahoma alone.
Twisters ripped up homes, a hospital and cut power to hundreds of thousands of people.
Oklahoma emergency officials said five people died after a tornado touched down yesterday in the town of Woodward, home to 12,000 people.
The storms were part of an exceptionally strong system that the Storm Prediction Centre in Norman, Oklahoma, had warned about for days.
At the storm's height, tornadoes popped up faster than they could be tallied. The centre's spokesman, Chris Vaccaro, said it had received at least 97 reports of tornadoes by dawn.
The outbreak began when tornado sirens went off before dawn in Oklahoma City on Saturday.