A powerful tornado blasted an area outside of Oklahoma City on Monday, leveling homes and killing at least 51 people.

CNN reported that at least seven of the dead were children from Plaza Towers Elementary School in Moore, which lay directly in the path of the monster storm’s wall of wind.

75 students and staff members had been huddled at the school when the storm hit, said the report.

As nightfall approached, determined searchers in hard hats dug in the debris for students possibly trapped, but authorities described the work as a recovery, not rescue, effort.

A temporary flight restriction was put in place over the school so that aircraft would stay away and emergency officials on the ground might hear any cries for help, said Lynn Lunsford with the Federal Aviation Administration.

The preliminary rating of damage created by the tornado is at least EF4 (winds 166 to 200 mph) — the second-most severe classification on a scale of zero to five — the National Weather Service said.

The tornado was estimated to be at least two miles wide at one point as it moved through Moore, according to CNN.

Twenty patients, including 12 adults and eight children, were in trauma rooms at Oklahoma University (OU) Medical Center and at the Children’s Hospital at OU Medical Center, spokesman Scott Coppenbarger told CNN.

Injuries ranged from minor to critical, he said.

Interstate 35 in Moore was closed as a result of debris from the tornado, Oklahoma Department of Transportation spokesman Cole Hackett said. Crews were heading to the north-south highway to start the cleanup process.

“People are trapped. You are going to see the devastation for days to come,” said Betsy Randolph, spokeswoman for Oklahoma Highway Patrol. She did not say how many people were trapped.

More than 38,000 electricity customers in Oklahoma are without power, according to local power providers.

The severe weather came after tornadoes and powerful storms ripped through Oklahoma and the Midwest earlier Monday and on Sunday.

Forecasters had said that the destructive weather, which killed at least two people, was perhaps just a preview.

Even before Monday afternoon’s devastation, residents in areas hard hit by weekend storms were combing through rubble where their homes once stood, reported CNN.

An estimated 300 homes were damaged or destroyed across Oklahoma in weekend weather, Red Cross spokesman Ken Garcia said.

Two men, both in their 70s, were confirmed dead as a result of an earlier tornado that hit Shawnee, the report said.

As many as 28 tornadoes were reported in Oklahoma, Kansas, Illinois and Iowa, according to the National Weather Service, with Oklahoma and Kansas the hardest hit.