Tornado "Lốc xoáy" tại Oklahoma City

Horror: Teachers carry children away from Briarwood Elementary school after a tornado destroyed the school in south Oklahoma City. The desperate search continued overnight for two dozen children feared dead after yesterday's monstrous tornado, which already took the lives of seven of their classmates

Shock: Two girls stand in rubble surveying the scene of devastation following the horrific tornado

Survivors: A child is pulled from the rubble of the Plaza Towers Elementary School in Moore, Oklahoma, and passed along to rescuers

Brave: Two boys are pulled from beneath a collapsed wall at the Plaza Towers Elementary School following a tornado in Moore, Oklahoma

Lucky ones: A young family comes out of underground bunker after the tornado to scenes of devastation

A boy is pulled from beneath a collapsed wall at the Plaza Towers Elementary School

Desperate: A young girl is pulled from beneath the wall by rescuers as they desperately search for more survivors at the school

Injured: Scores of young children were hurt in the monster twister that laid waste o the land. The walking wounded were helped to a nearby triage centre

Medical help: A woman carries an injured child to a triage center near the Plaza Towers Elementary School

Teachers carry children away from Briarwood Elementary school after a tornado destroyed the school in south Oklahoma City

Heroes: Rescue workers dig through the rubble of a collapsed wall at the Plaza Tower Elementary School to free trapped students

The number of children killed has not yet become clear as rescuers continue to move the rubble overnight

Help: A woman carries a child through a field near the collapsed Plaza Towers Elementary School in Moore

Poignant:  The devastating, two-mile-wide tornado touched down near Oklahoma City and wrecked havoc on the suburbs where lots of families lived

People look through the wreckage of their neighborhood after the tornado devastated the Oklahoma City suburb of Moore on Monday

Flattened: This aerial photo shows damage to the Plaza Towers Elementary School after massive tornado hit Moore, south of the city

Before the storm: An aerial photograph shows Plaza Towers Elementary School before it was hit by the monster tornado on Monday

Traumatic: A man sits down in shock in front of Plaza Towers Elementary school as seven children are found dead in a pool of water

Worst in memory: This detailed map of downtown Moore, Oklahoma, locates the path of Monday's devastating tornado and compares it to the path of the 1999 tornado, which had the most powerful winds ever recorded

This aerial photo shows the remains of homes hit by a massive tornado in Moore, Oklahoma, on Monday

Relief: Cindy Wilson texts to friends after her home was destroyed in the afternoon tornado. Cindy and her husband, Staff Sgt. B. Wilson, took cover in their home's bathtub when the tornado hit

Efforts: Rescue workers help free one of 15 people trapped in a medical building at the Moore hospital complex

This aerial photo shows the remains of houses in Moore after the tornado, which flattened entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school

Rescue workers help free one of the 15 people that were trapped at a medical building at the Moore hospital complex

Lost: People look for belongings after the tornado struck - President Barack Obama has declared a major disaster in Oklahoma

A fire burns in the Tower Plaza Addition in Moore, Oklahoma

Help: Emergency services move a woman to a car park after she is rescued from her home

Injured: A nurse helps an older man that suffered a head injury, left,  while another man is taken away from the IMAX theater that was used as a triage area

Rescue workers help free one of the 15 people that were trapped at a medical building at the Moore hospital complex after a tornado tore through the area

Through the night: A handout picture provided by the Oklahoma National Guard shows rescue personnel working to find survivors beneath rubble

Crews used jackhammers and sledgehammers to tear away concrete, and chunks were being thrown to the side as the workers dug.
National Guard choppers were being used across Moore overnight to detect body heat of survivors trapped under collapsed buildings and other rubble so they could direct rescuers.
Devastating aerial images taken immediately after the tornado show Plaza Towers - as well as hundreds of homes and businesses - completely leveled with cars thrown into the school grounds by the powerful storm.
Students who were inside the building described clinging to the walls of the hallway where many of them huddled during the storm as the twister battered the school. Others cowered in closets or bathrooms to protect themselves.

One sixth grade boy named Brady told ABC affiliate KOCO-TV in Oklahoma City that he and other students took cover in the boys' bathroom.
'Cinderblocks and everything collapsed on them but they were underneath so that kind of saved them a little bit, but I mean they were trapped in there,' he said.
Frightened third graders were being pulled from the wreckage alive this afternoon as rescue workers passed the children down a human chain before taking them to a triage center set up in the school's parking lot.
Staff said there had been at least 75 people in the school of around 500 students when the tornado hit. The 4th, 5th, and 6th grade students were taken from the school to a church before the twister barreled through. One teacher said she had laid on six children to protect them. It is believed another teacher put her life at risk to cover three students and suffered serious injuries. It is unclear whether she survived.

Taking it in: A boy sits on the trunk of a car outside a house which has been wrecked in the storm

Past: In May 1999 , the town of Moore was hit by a severe tornado which had the highest winds ever recorded on Earth

Last one standing: Dana Ulepich searches inside a room left standing at the back of her house which was destroyed

Kay James holds her cat as she sits in her driveway after her home was destroyed by the tornado that hit the area on Monday

Workers continued to dig through the rubble of Plaza Towers Elementary School on Monday afternoon

Horror: Local residents look through the debris that remains where homes once stood

Twisted metal and debris lie in the parking lot in front of an IMAX theatre as an American flag stands proudly in the wind

Moore police dig through the rubble of the Plaza Towers Elementary School following a tornado in Moore

Decimated: A truck lays damaged in a field near the Moore Medical Center, background, after a tornado moves through Moore

A damaged police car in the midst of debris from the violent storm that lasted 45 minutes

Force: The upturned cars show the full force of the storm which ripped through the suburbs

Chaos: Dozen of cars piled up on top of each other in the parking lot of Moore Hospital

Site: A map shows where the worst tornado damage was sustained in Moore, Oklahoma on Monday. The red triangles show the areas hit

Paths: This map shows the paths of tornadoes over the years in the Moore, Oklahoma area, with red showing the May 3rd, 1999 tornado path; blue the May 8th, 2003 tornado path and green the May 20th, 2013 tornado path You can see how a portion of the 2013 storm (green) overlaps the 1999 storm (red), which was an F5 tornado that did around 1.1 billion dollars in damage. 36 people died in that storm and 8,000 homes were badly damaged or destroyed.

A Moore resident took a picture of the monstrous twister as it barreled towards the heavily-populated Oklahoma City suburb

A monstrous tornado roared through the Oklahoma City suburbs, flattening entire neighborhoods with winds up to 200 mph, setting buildings on fire and landing a direct blow on an elementary school

The EF-4 tornado as it approached the town of Moore, Oklahoma, near Oklahoma City, on May 20

THE SCIENCE BEHIND THE STORM: HOW DID IT HAPPEN?

The severe thunderstorms that produce tornadoes form where cold dry air meets warm moist tropical air.
The wind coming into the storm starts to swirl and forms a funnel. The air in the funnel spins faster and faster and creates a very low pressure area which sucks more air - and objects on the ground into it.
Most tornadoes spin cyclonically (counter-clockwise) in the Northern hemisphere.
The twisters are most common in a section of the U.S. called Tornado Alley, with most forming in the months of April and May.
The vortex of winds varies in size and shape, and can be hundreds of meters wide.
There are, on average, 1,300 tornadoes each year in the United States, which have caused an average of 65 deaths annually in recent years.
Conditions on the ground do not generally affect the power of a tornado, including terrain and structures like buildings.
Moore, Oklahoma is within the boundaries of Tornado Alley, which includes northern Texas, Oklahoma, Kansas, Nebraska and South Dakota.
The city was the site of another devastating tornado that tore through the town in 1999.

Speaking outside Norman Regional Hospital Ninia Lay, 48, said she huddled in a closet through two storm alerts and the tornado hit on the third.
'I was hiding in the closet and I heard something like a train coming,' she said under skies still flashing with lightning. The house was flattened and Lay was buried in the rubble for two hours until her husband Kevin, 50, and rescuers dug her out.
'I thank God for my cell phone, I called me husband for help.'
Her daughter Catherine, seven, a first-grader at Plaza Towers Elementary School, took shelter with classmates and teachers in a bathroom when the tornado hit and destroyed the school. She escaped with scrapes and cuts.Oklahoma City Police Capt. Dexter Nelson warned that downed power lines and open gas lines posed a risk in the aftermath of the system.
A KFOR reporter says that doctors told her of looting at the hospital damaged by the tornado.
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, pieces of insulation, awnings, shingles and glass all over the streets.
Volunteers and first responders raced to search the debris for survivors.
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.
'The whole city looks like a debris field,' Glenn Lewis, the mayor of Moore, told NBC.
'It looks like we have lost our hospital. I drove by there a while ago and it's pretty much destroyed,' Lewis said.

James Rushing, who lives across the street from Plaza Towers Elementary School heard reports of the approaching tornado 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.
Douglas Sherman drove two blocks from his home to help rescue survivors.
'Just having those kids trapped in that school, that really turns the table on a lot of things,' he said.

Rescuers recover a horse from the remains of a day care center and destroyed barns

Workers look for victims under debris from a tornado that passed across south Oklahoma City

Glenn Rusk hugs his neighbor Sherie Loman outside her home north of Briarwood Elementary School after a tornado moved through the area

A destroyed house remains after a huge tornado struck Moore, Oklahoma, near Oklahoma City

Aftermath: Fires have also broken out at buildings after the monster storm thanks to exposed power lines, CNN reported

Twisted metal lies in the road as people take pictures of damage after a huge tornado struck on Monday

A woman is comforted after a tornado that destroyed buildings and overturned cars struck Moore

A woman walks through debris after a huge tornado struck Moore, Oklahoma, near Oklahoma City, May 20, 2013

A sign for a local restaurant lies on the ground after a huge tornado struck Moore, Oklahoma, near Oklahoma City

An American flag sits among devastation after the massive twister barreled through Moore, Oklahoma

Debris hangs from a tree over a destroyed home as Abby Madi and Peterson Zatterlee comforts Zaterlee's dog Rippy after escaping the brunt of the storm

Scale: Bewildered residents assess the damage in their neighborhood