Search-and-rescue crews worked through the night after a monstrous tornado barreled through the Oklahoma City suburbs, demolishing an elementary school and reducing homes to piles of splintered wood. At least 24 people were killed, including at least seven children, and those numbers were expected to climb.
As the sun rose over the shattered community of Moore, the state medical examiner's office cut the estimated death toll by more than half.
Spokeswoman Amy Elliot said she believes some victims were counted twice in the early chaos of the storm. Downed communication lines and problems sharing information with officers exacerbated the problem, she said.
Authorities initially said as many as 51 people were dead, including 20 children.
Some 236 people were hurt, and that number was also expected to rise. It included some 50 children. By early morning, the search and rescue operation there had turned to a recovery effort as first responders picked through mountains of debris, reports CBS News correspondent Bigad Shaban.
In Washington, President Barack Obama pledged urgent government help for Oklahoma Tuesday in the wake of "one of the most destructive" storms in the nation's history.
"In an instant neighborhoods were destroyed, dozens of people lost their lives, many more were injured," Obama said from the White House State Dining Room. "Among the victims were young children trying to take shelter in the safest place they knew - their school."
The president added that the town of Moore "needs to get everything it needs right away."
Sen. Tom Coburn, R-Okla, said: "I spoke with Department of Homeland Secretary Janet Napolitano last night about FEMA's response. We still don't know the scope of devastation and won't for some time. As the ranking member of Senate committee that oversees FEMA, I can assure Oklahomans that any and all available aid will be delivered without delay."
The ferocious storm -- less than 1 percent of all tornadoes reach such wind speeds -- ripped through the suburb of Moore in the Midwest region known as Tornado Alley. Severe weather warnings were posted in much of the region Tuesday morning.
The storm laid waste to scores of buildings in Moore, a community of 41,000 people about 10 miles south of Oklahoma City. Block after block lay in ruins. Homes were crushed into piles of broken wood. Cars and trucks were left crumpled on the roadside. Rescuers launched a desperate rescue effort at the elementary school, pulling children from heaps of debris and carrying them to a triage center.
Some two dozen children were unaccounted for Tuesday morning, CBS News correspondent Anna Werner says.
Crews have brought cadaver dogs to search for children trapped under the rubble, reports CBS Oklahoma City affiliate KWTV.
Overnight, Oklahoma City police asked media members to clear out of the vicinity of the school. "(Law enforcement officials) are securing the entire area -- media, homeowners, everyone," Oklahoma City Police Sgt. Jeremy Lewis explained to CBS News. "There are still gas leaks as of right now. We have hundreds of officers in there doing searches by grid trying to locate people who are still in debris. ... We have natural gas everywhere. Natural gas is just spewing."
The National Weather Service estimated that the tornado reached up to a half-mile wide and was an EF-4 on the enhanced five-point Fujita scale, the second most powerful type of twister.
Amy Elliott, spokeswoman for the Oklahoma Medical Examiner's Office, told The Associated Press early Tuesday that officials could see as many as 40 more fatalities as a result of tornado in addition to the 51 already confirmed dead. She said at least 20 children were among the confirmed dead.
In videos 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.
Oklahoma Gov. Mary Fallin deployed 80 National Guard troops to assist with rescue operations and activated extra highway patrol officers.
Fallin also spoke with President Obama, who declared a major disaster and ordered federal aid to supplement state and local recovery efforts. The president is expected to address the nation around 10 a.m. ET on Tuesday.
"Hearts are broken" for parents looking for their children, Fallin told a news conference.
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.
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.
Country music star Toby Keith, who grew up in Moore, said his hometown would persevere.
"Hometown got hit for the gazillionth time. Rise again Moore Oklahoma," Keith tweeted Monday evening.
Pope Francis tweeted a message of concern for the victims, saying: I am close to the families of all who died in the Oklahoma tornado, especially those who lost young children. Join me in praying for them."
Queen Elizabeth II said she was "deeply saddened" by the loss of life and devastation caused by the tornado in Oklahoma and sent her "deepest sympathies" to all those whose lives have been affected.
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.
Eventually, Denton said, his sons spotted him in the crowd. They were fine, but upset to hear that their grandparents' home was destroyed.
As dusk began to fall, heavy equipment was rolled up to the school, and emergency workers wearing yellow crawled among the ruins.
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.
Many land lines to stricken areas were down, and cell phone networks were congested. The storm was so massive that it will take time to establish communications between rescuers and state officials, the governor said.
Tiffany Thronesberry said she heard from her mother, Barbara Jarrell, shortly after the tornado struck.
"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.
The tornado also destroyed the city hospital and numerous businesses. Moore Mayor Glenn Lewis watched it pass through from his jewelry shop.
"All of my employees were in the vault," Lewis said.
Lewis, who was also the mayor of Moore when the strongest tornado on record whipped the city in 1999, said the most recent storm won't deter the community from rebuilding.
Lewis said this year's twister was bigger than one that hit in 1999, though its winds were not as strong. Lewis said the cleanup has already started, and that city workers were already at work printing new street signs to replace those that blew away.
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.
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. local timeWhen 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.
Monday's powerful tornado loosely followed the path of the killer twister that slammed Moore in May 1999. That storm produced the highest winds ever recorded near the Earth's surface - 302 mph.
Kelsey Angle, a weather service meteorologist in Kansas City, Missouri, 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.
"Oklahoma City has had more tornado strikes than any other city in the United States," the city government's website says.
Monday's devastation in Oklahoma came almost exactly two years after an enormous twister ripped through the city of Joplin, Missouri, killing 158 people and injuring hundreds more. On Monday, Joplin organized a team of about a dozen police and firefighters to assist in Moore.
Joplin City Manager Mark Rohr said his community remembers the assistance it received in 2011 and feels an obligation to lend a hand in Moore.
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, Michigan, when 116 people died.