A monstrous tornado at least a half-mile wide roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods and destroying an elementary school with a direct blow as children and teachers huddled against winds up to 200 mph.
At least 51 people were killed, and officials said the death toll was expected to rise. The Oklahoma Medical Examiner's Office told NBC News late Monday night that at least 20 of the 51 fatalities accounted for so far are children.
The storm laid waste to scores of buildings in Moore, a community of 41,000 people about 10 miles south of the city. Block after block lay in ruins. Homes were crushed into piles of broken wood. Cars and trucks were left crumpled on the roadside.
The National Weather Service issued an initial finding that the tornado was an EF-4 on the enhanced Fujita scale, the second most-powerful type of twister.
The scene in Moore has been described simply as "total devastation."
KFOR-TV's news helicopter followed along as the massive tornado cut a large swath leading up to and through Moore. The tornado was estimated to be on the ground for about an hour, cutting a swath 20 miles long and about 1 mile wide. The debris ball is estimated to be at least two miles wide.
More than 140 people were being treated at hospitals, including about 70 children. And search-and-rescue efforts were to continue throughout the night.
Tiffany Thronesberry said she heard from her mother, Barbara Jarrell, shortly after the tornado.
"I got a phone call from her screaming, `Help! Help! I can't breathe. My house is on top of me!"' Thronesberry said.
Thronesberry hurried to her mother's house, where first responders had already pulled her out. Her mother was hospitalized for treatment of cuts and bruises.
Rescuers launched a desperate rescue effort at the school, pulling children from heaps of debris and carrying them to a triage center.
Oklahoma Gov. Mary Fallin deployed 80 National Guard members to assist with rescue operations and activated extra highway patrol officers.
Fallin also spoke with President Barack Obama, who offered the nation's help and gave Fallin a direct line to his office.
Many land lines to stricken areas were down, and cellphone networks were congested. The storm was so massive that it will take time to establish communications between rescuers and state officials, the governor said.
In video of the storm, the dark funnel cloud could be seen marching slowly across the green landscape. As it churned through the community, the twister scattered shards of wood, awnings and glass all over the streets.
Chris Calvert saw the menacing tornado from about a mile away.
"I was close enough to hear it," he said. "It was just a low roar, and you could see the debris, like pieces of shingles and insulation and stuff like that, rotating around it."
Even though his subdivision is a mile from the tornado's path, it was still covered with debris. He found a picture of a small girl on Santa Claus' lap in his yard.
Volunteers and first responders raced to search the debris for survivors.
At Plaza Towers Elementary School, the storm tore off the roof, knocked down walls and turned the playground into a mass of twisted plastic and metal.
Children from the school were among the dead, but several students were pulled alive from the rubble. Rescue workers passed the survivors down a human chain to the triage center in the parking lot.
KFOR's Lance West reported at about 6:30 p.m. that the search at the school had turned from a search and rescue into a recovery effort.
Seven children found drowned in a pool of water at Plaza Towers are among the 51 killed in the storm, the state medical examiner's office told NBC News.
James Rushing, who lives across the street from the school, heard reports of the approaching twister and ran to the school, where his 5-year-old foster son, Aiden, attends classes. Rushing believed he would be safer there.
"About two minutes after I got there, the school started coming apart," he said.
The students were sent into the restroom.
There are multiple reports of teachers laying on children and using their body to protect them from flying debris.
The tornado also destroyed Briarwood Elementary School.
A man with a megaphone stood near a Catholic church Monday evening and called out the names of surviving children. Parents waited nearby, hoping to hear their sons' and daughters' names.
Don Denton hadn't heard from his two sons since the tornado hit the town, but the man who has endured six back surgeries and walks with a severe limp said he walked about two miles as he searched for them.
As reports of the storm came in, Denton's 16-year-old texted him, telling him to call.
"I was trying to call him, and I couldn't get through," Denton said.
As dusk began to fall, heavy equipment was rolled up to the school, and emergency workers wearing yellow crawled among the ruins, searching for survivors.
Because the ground was muddy, bulldozers and front-end loaders were getting stuck. Crews used jackhammers and sledgehammers to tear away concrete, and chunks were being thrown to the side as the workers dug.
Douglas Sherman drove two blocks from his home to help.
"Just having those kids trapped in that school, that really turns the table on a lot of things," he said.
A map provided by the National Weather Service showed that the storm began west of Newcastle and crossed the Canadian River into Oklahoma City's rural far southwestern side about 3 p.m. When it reached Moore, the twister cut a path through the center of town before lifting back into the sky at Lake Stanley Draper.
Oklahoma City Police Capt. Dexter Nelson said downed power lines and open gas lines posed a risk in the aftermath of the system.
Spokeswoman Brooke Cayot said nine of 57 patients who are being treated at the Integris Southwest Medical Center were listed in critical condition after Monday afternoon's tornado. Nineteen were in serious condition and 29 were listed in fair or good condition.
She said five of the patients were children who have since been treated and released.
OU Medical Center spokesman Scott Coppenbarger said his hospital and a nearby children's hospital are treating approximately 85 patients, including 65 children.
He said those patients ranged from minor injuries to critical condition.
The tornado hit a small hospital in Moore, but all of the 30 patients inside "amazingly" survived.
Moore Medical Center spokeswoman Kelly Wells said the hospital was "pretty much destroyed." All of the 30 patients survived, as did all of the staff members at the 46-bed acute care hospital, she said.
Wells said 13 patients were transferred to other facilities, though it wasn't clear if they were moved because of injuries sustained in the tornado or because of existing medical conditions.
Texas Gov. Rick Perry released the following statement after learning of the horrific devastation in Moore.
"The images emerging from Oklahoma today are a terrifying reminder of how quickly the force of Mother Nature can devastate entire communities. Our hearts are heavy for all Americans who have been affected by the recent outbreak of storms across our country. State emergency assets in Texas will remain on alert and stand ready to help our neighbors any way we can."
KFOR meteorologist Mike Morgan estimates the tornado to be an EF-5 in strength (peak wind speeds greater than 200 mph) and the damage about three times as bad as the May 3, 1999, tornado that tore through the same town. That 1999 tornado had the highest winds ever recorded near the earth's surface.
Morgan also said about 30 square miles have been affected by damage.
Monday's powerful tornado loosely followed the path of a killer twister that slammed the region in May 1999.
The weather service estimated that Monday's tornado was at least a half-mile wide. The 1999 storm had winds clocked at 300 mph.
Kelsey Angle, a weather service meteorologist in Kansas City, Mo., said it's unusual for two such powerful tornadoes to track roughly the same path.
It was the fourth tornado to hit Moore since 1998. A twister also struck in 2003.
Monday's devastation in Oklahoma came almost exactly two years after an enormous twister ripped through the city of Joplin, Mo., killing 158 people and injuring hundreds more.
That May 22, 2011, tornado was the deadliest in the United States since modern tornado record keeping began in 1950, according to the National Oceanic and Atmospheric Administration. Before Joplin, the deadliest modern tornado was June 1953 in Flint, Mich., when 116 people died.