UPDATE - 4:05 pm - There is a swath of heavy destruction from Newcastle- through extreme southern Oklahoma City into the city of Moore OK..
There are as of yet an unknown number of injuries- but many dozens of homes and buildings have been destroyed by what looks on TV news chopper pictures as a high EF-4 or EF-5 tornado.
At least two schools- whose students were "on lockdown until the tornado passed-" have been heavily damaged as well as the Moore Medical Center.
A caller to one of the OKC TV stations said citizen rescuers "were pulling 3rd graders" from the rubble of the demolished "Plaza Towers" Elementary school building.
Rescuers were still trying to reach a reported "40 students unaccounted for as well as two janitors (KFOR4)" at Plaza Towers late Monday evening.
Struck first and heavily-damaged was the Briarwood Elementary school.
KFOR reported at 9:44 pm that there "were no fatalities at Briarwood" school- although a yet-unknown number of children and faculty were injured.
As of 5:30 pm- "19 patients" were reported to be at the Moore Medical Center (MMC)- itself damaged by the tornado.
There was at least six serious to critical injuries at that medical facility- but no serious injuries reported inside MMC itself when the tornado smashed into the building at 3:24 pm.
A fairly recently-built Warren movie theater complex just south of MMC also took a direct hit- but the building survived remarkably barely damaged.
Around 100 people rode out the twister inside the theater's hallways.
At S.W. 4th Street and Telephone Road across from MMC- citizen rescuers- including a KFOR TV reporter- dug into the debris of what had been a 7-11 convenience store only to find a 3-month-old infant and it's mother dead- along with another man.
It was reported the woman and child had sought shelter from the tornado in 7-11's coolers.
As of 5:50 pm- KFOR is reporting "4 fatalities."
Within 15 minutes- that total had been increased to "six."
As of 10 pm- the death toll is reported as "51 - 20 of those were children" according to KOCO-TV.
More than 260 injured were reported at various medical facilities in Metro OKC.
The KFOR-4 meteorologist Mike Morgan at 4:18 pm said "the damage from (today's) tornado dwarfs (the damage) of the May 3, 1999" tornado that struck Moore.
The tornado's radar-indicated "debris ball" was estimated as "2-1/2-miles wide-" although the tornado funnel itself was 1.3 miles wide according to the NWS on Tuesday.
As a historic aside- today is the 56th anniversary of Metro Kansas City's infamous "Ruskin Heights Tornado."