MOORE, Okla. -- Survey crews for the National Weather Service say it's possible the tornado that hit Moore Monday was an EF-5 at some point while on the ground.
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The NWS Norman office reported Tuesday afternoon at least one area received EF-5 damage. It took crews until late Tuesday morning to reach the hardest-hit areas.
On Monday evening the NWS issued a preliminary rating of EF-4 for the storm with winds near 200 miles per hour.
According to the preliminary report, the tornado was on the ground for a distance of about 17 miles and the greatest width of damage was at 1.3 miles wide.
The death toll from the tornado stands at 24 people, including nine children.
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Authorities said initially that as many as 51 people were dead, including 20 children. Oklahoma State Medical Examiner's office spokeswoman Amy Elliot said Tuesday morning that she believes some victims were counted twice in the early chaos of the storm.
Elliot said during a press conference they believe the death toll will increase.
Citing officials with the Oklahoma Highway Patrol, our NBC affiliate in Oklahoma City, KFOR, reported early Tuesday morning that search crews found 101 people alive overnight amid the rubble.
Rescue crews were well underway on a second sweep of affected neighborhoods, focusing on storm shelters where people may be trapped. The goal is to search every area three times.
The tornado flattened homes and hit two elementary schools head-on around 3 p.m. Monday.
All students of Briarwood Elementary School in Moore were accounted for by Monday evening.
The search and rescue effort at Plaza Towers Elementary School transitioned to a recovery effort hours after the storm. Seven children there were found dead in a pool of water in the elementary school rubble. Moore police said Tuesday everyone at the school had been accounted for.
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Moore Medical Center sustained significant damage. All 13 patients there were apparently transferred to other facilities.
President Barack Obama declared a major disaster in Oklahoma late Monday night and ordered federal aid to supplement state and local recovery efforts.