Winds of up to 200 mph tore through Oklahoma City and its suburbs on Monday afternoon, flattening homes, flinging cars through the air and crushing at least two schools.
Medical officials said 233 people had been injured and more than 120 were being treated at hospitals, including 50 children.
Rescuers walked through neighborhoods to see if they could hear any voices calling out from the rubble.
Before them was a scene of devastation, as the twister flattened home after home, flipped over vehicles, and left massive piles of shredded cinder block, insulation and metal.
Families anxiously waited at nearby churches to hear if their loved ones were A man with a megaphone stood Monday evening near St.
Andrews United Methodist Church and called out the names of surviving children.
Parents waited nearby, hoping to hear their sons' and daughters' names. The Plaza Towers primary school with children sheltering inside was razed.
Rescuers managed to pull at least 30 of the estimated 75 children from the wreckage of the school, but at least two dozen more were believed to be inside, Most of them are feared to have died when the tornado struck.
In one amazing example of bravery, six children were saved when their teacher, who sustained serious injuries, used her body to sheild them.
Amy Elliott, the spokeswoman for the Oklahoma City medical examiner, confirmed that at least 91 people had died, including the children, and officials said that toll was likely to climb.
Hospitals reported at least 145 people injured, 70 of them children. She was later pulled out of the ruins of her home alive.