1:09pm: We'll wrap up our live coverage of the tornado in Oklahoma City now. Here's a story with the latest details, which we will continue updating throughout the day. 12:28pm: The National Weather Service said the tornado generated winds of up to 321km/h. "It's certainly the most powerful tornado that I've ever dealt with in my 20 years with the weather service," NWS meteorologist Rick Smith in Norman, Oklahoma, told the BBC. Oklahoma Governor Mary Fallin said it was a "tragic" day and "hearts are broken" for parents looking for their children. 12:14pm: The course of the latest tornado is remarkably similar to one that struck the same area on May 3, 1999. The National Weather Service has plotted the course of both tornadoes on the map below: Source: National Weather Service 11:58am: A resident of a flattened suburb near Oklahoma City recorded this footage on his mobile phone as he walked through the devastated streets: 11:51am: There's some good news from a second elementary school near Oklahoma City, where all students and staff have been accounted for. Initially there were fears of casualties at Briarwood Elementary School, but that is not the case, according to local station KFOR-TV. It's a different scenario at the nearby Plaza Towers Elementary School. Seven students reportedly drowned while sheltering in that school's basement, according to a report that has not been independently confirmed. As darkness sets in, rescuers have set up giant floodlights as they search for more victims in the rubble at Plaza Towers. 11:20am: The National Oceanic and Atmospheric Administration has compiled this list of the deadliest tornadoes since 1900: 695 deaths. March 18, 1925, in Missouri, Illinois and Indiana 216 deaths. April 5, 1936, in Tupelo, Mississippi 203 deaths. April 6, 1936, in Gainesville, Georgia 181 deaths. April 9, 1947, in Woodward, Oklahoma 158 deaths. May 22, 2011, in Joplin, Missouri 143 deaths. April 24, 1908, in Amite, Louisiana, and Purvis, Mississippi 116 deaths. June 8, 1953, in Flint, Michigan 114 deaths. May 11, 1953 in Waco, Texas May 18, 1902 in Goliad, Texas 103 deaths. March 23, 1913, in Omaha, Nebraska Source: National Oceanic and Atmospheric Administration 11:09am: The death toll from the Oklahoma tornado has just been revised up to 51. Children are among those dead, the state medical examiner's office has confirmed. 10:53am: It's approaching 8pm in Oklahoma City, and authorities are setting up floodlights at the site of Plaza Towers Elementary School where there are reports of up to 30 children still missing. The state medical examiner's office says 37 people now have been confirmed dead. Local station KFOR is reporting that seven children drowned in the basement of the Plaza Towers school. That number has not been independently confirmed. Searchers in hard hats are digging in the debris looking for survivors. 10:47am: More photos are filtering through from Oklahoma City. We'll be updating this gallery throughout the day: 10:44am: The same suburb, Moore, was hit hard by a tornado in 1999. AP says that storm had the distinction of producing the highest winds ever recorded near the Earth's surface - 486 km/h. Tornadoes frequently touch down on Oklahoma's wide open plains, but the fact that Monday's twister struck a populated urban area raised fears of a high casualty toll. 10:37am: President Barack Obama has called Oklahoma Governor Mary Fallin to express his concern, according to a statement from the White House. President Obama told the governor that he had directed the government and the Federal Emergency Management Agency to provide any assistance needed. FEMA has sent a special team to Oklahoma's emergency operations centre to dispatch resources. 10:27am: Some of the reports coming out of the Oklahoma City are terrifying. Children told local media that they had to hold on to walls as the tornado tore through their school. Thousands of people, some partly clothed and apparently caught by surprise, are reportedly walking north from the worst of the devastation. A car pile-up outside Moore, Oklahoma, following a destructive tornado on Monday, May 20, 2013. 10:23am: Here's an overview of how the tornado struck. It touched down at 2.56pm local time and travelled for 32 kilometres, Keli Pirtle, a spokeswoman for the National Weather Service in Norman, told the New York Times. The tornado was on the ground for 40 minutes. It struck the town of Newcastle and travelled for about 16 kilometres to Moore, a heavily populated suburb of Oklahoma City. Preliminary data suggests that it was category four tornado on the Enhanced Fujita scale, which measures tornado strength on a scale of 0 to 5. A definitive assessment will not be available until tomorrow. 10:19am: The toll from the tornado in Oklahoma City is rising rapidly. The state medical examiner's office says 37 people now have been confirmed dead, and the toll is expected to rise. 10:11am: Local television station KFOR is reporting that authorities on the scene have confirmed the deaths of seven children in Plaza Towers Elementary School. The children reportedly drowned in the basement of the school while sheltering from the storm, according to KFOR. Source: AP 10:02am: This size of the destruction is vast, according to local television station KFOR. The tornado was believed to be on the ground for 30 kilometres. It was up to three kilometres wide, and has caused nearly 50 square kilometres of devastation. Early reports suggest it was worse than another devastating tornado that struck the same area in May, 1999. Homes are completely flattened outside Moore, Oklahoma. 9:55am: The two elementary schools that were hit by the are Plaza Towers Elementary School and Briarwood Elementary School. Plaza Towers was the worst hit. ""There are 13 kids that are buried right now,"" Senator James Inhofe, an Oklahoma Republican, said in an interview in Washington. At least 75 students were in the school at the time, local TV station KFOR reported. As many as 30 may have been rescued, the station said. 9:44am: Our US correspondent, Nick O'Malley, has the latest on the huge tornado that struck Oklahoma City's suburbs. He says at least one primary school has been obliterated by the tornado nearly two kilometres wide, leaving an unknown number of children and teachers trapped, injured and perhaps killed. The storm, with winds up to 267 kilometres per hour, was so violent that it flattened neighbouring homes, stripping parts of the suburb not only of its homes, cars, trees and shrubs, but according to some reports, even of its grass. At present emergency workers, National Guard troops and volunteers are searching for survivors in the school and its surrounds. Nick will be updating this story as the day progresses. 9:34am: CNN is reporting at least six people have been killed in the tornado. There are also reports several children have been pulled out of rubble alive at a primary school in Moore, which is south of the city. Rescue workers lifted children from the rubble before they were passed down a human chain and taken to a triage center set up in the school's parking lot. 9:26am: Some of the early photographs coming out of the Oklahoma City suburbs show the extent of the destruction. Entire blocks appear to have been razed. We'll be adding to this gallery throughout the morning.