At least 91 people have been declared dead, a lot of them children, after a giant tornado measuring at least a mile wide ravaged through the highly populated portions of Oklahoma City and surrounding suburbs on Monday.

The devastating tornado, which is said to be larger than the destructive storm that damaged the same area in 1999, left harrowing images of flattened homes, tossed cars, and crushed buildings, including at least two schools.

As several injured residents stormed nearby hospitals, authorities said more people remained trapped even as rescue workers continue to wrestle through the debris laden streets leading to the suburb of Moore which was the most severely hit.

Latest reports from the Oklahoma City medical examiner indicate that at least 91 people had died, many are children, and the numbers according to officials were still likely to rise as rescue operations continue. According to the latest reports of local hospitals, number of injured people has reached 145 of which 70 are children.

On Monday afternoon, several children were pulled out from the rubble that transformed Moore's Plaza Towers Elementary School into a mountain of wrenched metals and felled walls. On Monday evening, however, crews began having difficulty piercing through downed beams and debris as rescue continued for dozens more students reportedly still trapped inside the building.

Meanwhile, at Briarwood Elementary School in Oklahoma City, seen were cars flung through the building facade and the roof completely blown off.

"Numerous neighborhoods were completely leveled," said Sgt. Gary Knight of the Oklahoma City Police Department. "Neighborhoods just wiped clean." He said emergency rescuers were being hindered mostly by the debris and the damaged roadways and also the heavy traffic.

According to Keli Pirtle, National Weather Service spokesperson in Norman, Oklahoma, the tornado landed at around 2:56 p.m. on Monday, about 16 minutes after the first warning sounded off. It travelled 20 miles and was aground for about 40 minutes. It hit the town of Newcastle and went straight 10 miles to Moore, a densely populated portion of Oklahoma City.

Preliminary information indicated that the tornado was under Category 4 based on the Enhanced Fujita scale, according to Ms. Pirtle. She said a more conclusive finding will be available on Tuesday.

In May 1999, Moore was also struck by a giant tornado with winds recorded at a speed of 302 mph.

Monday news on television reported the devastation that covered a wide area, with images of piles upon piles of debris, flattened homes and destroyed businesses. Several structures were seen on fire, cars flinging through the air and piling up on top of each other.

One resident Kelcy Trowbridge recounted how she and her family rushed and piled into the cellar of their neighbour just outside of Moore, and for around five minutes gathered together under a blanket as the tornado howled above them, with debris banging forcefully against the cellar door.

When they came out, they found their house completely flattened and their car was down the road in an upside down position. It was then that her husband asked her to call the police after assessing what was left of their property.

Then she recalled the heart-wrenching moment when her husband found the body of a little girl about 2 to 3 years old.

"He knew she was already gone," Ms. Trowbridge said. "When the police got there, he just bawled."

"My neighborhood is gone. It's flattened. Demolished. The street is gone. The next block over, it's in pieces," she said.

It may not be fully over yet as the storm system continued to alert across the region on Monday afternoon. Forecasters have warned residents of the possibility of new tornadoes forming.

According to Russell Schneider, director of the National Oceanic and Atmospheric Administration's Storm Prediction Center in Norman, Oklahoma, the area remains on heightened alert going into Tuesday as the probability of tornadoes throughout the region is still high.