THUNDERSTORMS and tornadoes tore across the U.S. states of Missouri, Oklahoma and Georgia on Saturday evening, killing at least 20 people.

Oklahoma Gov. Brad Henry issued a statement saying a major emergency response was under way. He planned to visit the area later.

“Our thoughts and prayers are with all of the Oklahoma communities that have been impacted by the latest wave of severe weather,” Henry said.

At least 12 people were killed after severe storms spawned tornadoes and high winds across sections of southwestern Missouri, the State Emergency Management Agency (SEMA) said.

“They’re going over the hard-hit area and turning over everything and looking,” SEMA spokeswoman Susie Stonner said of emergency workers’ search for victims and assessment of damage. “It’s hard to do in the dark.”

The number of injuries across the area was not immediately available, though The Joplin (Mo.) Globe reported that more than 90 people from that region were being treated at Joplin hospitals.

Television footage showed some destroyed outbuildings and damaged homes west of McAlester and near Haywood. At a glass plant southwest of McAlester, the storm apparently picked up a trailer and slammed it on top of garbage bins.

“These are rural areas that we are in,” Pittsburg County Undersheriff Richard Sexton told KFOR-TV in Oklahoma City. “These are good people coming together at this time.”

In storm-weary Arkansas, a tornado collapsed a home and a business, and there were reports of a few people trapped in buildings, said Weather Service meteorologist John Robinson.

Central Park Elementary School in the northwest Arkansas city of Bentonville had roof and window damage, and damage was also reported at Pine Creek Center School.

The storms remained active into the night as they swept eastward, with watches and warnings abundant across a wide swath of the Plains and South.

Rescuers freed a man trapped in his vehicle in western Tennessee after a tree fell on it during thunderstorms, Memphis firefighters said.

Memphis authorities said they had received reports of power lines and trees down, but there had been no injuries.

Tornadoes killed 13 people in Arkansas on Feb. 5, and another seven were killed in an outbreak May 2.

(SD-Agencies)