MOORE, Okla. — A giant tornado, a mile wide or more, killed at least 91 people, 20 of them children, as it tore across parts of Oklahoma City and its suburbs Monday afternoon, flattening homes, flinging cars through the air and crushing at least two schools.

The injured flooded into hospitals, and the authorities said many people remained trapped, even as rescue workers struggled to make their way through debris-clogged streets to the devastated suburb of Moore, where much of the damage occurred.

Amy Elliott, the spokeswoman for the Oklahoma City medical examiner, said 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.

Plaza Towers Elementary School in Moore was reduced to a pile of twisted metal and toppled walls. Rescue workers were able to pull several children from the rubble, but on Monday evening crews were still struggling to cut through fallen beams and clear debris amid reports that dozens of students were trapped. At Briarwood Elementary School in Oklahoma City, on the border with Moore, cars were thrown through the facade and the roof was torn off.