The number of people killed in a tornado in Oklahoma City in the US has been revised down from 91 to 24. The office of the State medical examiner believes some of the victims were counted twice in the early chaos of the storm. The victims include 7 children.

The US President Barack Obama is due to make a statement following the tornado, but has already sent a message out through Twitter

"Our prayers are with the people of Oklahoma today."—President Obama

— Barack Obama (@BarackObama) May 21, 2013

The town of Moore was given a 16 minute warning before the 2-mile wide twister hit the ground.

The ferocious tornado flattened entire neighbourhoods in the southern suburb of Moore, Oklahoma with winds of up to 200 mph rendering thousands of people homeless, leaving buildings on fire and landing a direct blow to a school.

Several children were pulled alive from the wreckage of Plaza Towers Elementary School after the devastating, mile-wide tornado reduced the building to heap of rubble and twisted metal.

Pictured above: Plaza Towers elementary school was located in a residential area 

Rescuers passed the children down a "human chain" to get them to medical personnel for treatment.

Roughly 500 students attend the school. It is unclear whether any had been evacuated before the twister hit but local media reported some children were taken to a nearby church.

A second elementary school, Briarwood, was also hit but did not appear to have sustained casualties. Moore's hospital was also badly damaged.

Emergency crews pledged to work through the night across the city to look for survivors, amid reports that another, smaller, storm was on its way to the town of 55,000 people.

Hospital worker Brook Cayot discusses treating victims of the tornado.